Basic Computer Troubleshooting Tasks

This is one of the most important and basic computer tasks. BIOS stands for Basic Input/Output System. It runs the computer when it is first powered-on before handing control over to the operating system (Linux, Windows, Mac OSX, etc.). The boot order is the order in which the BIOS searches devices for an operating system to start, or boot from. Valid boot devices include hard drives, optical (CD or DVD) drives, floppy drives, USB flash drives, and some computers can boot from a network.
When you first start or restart your computer a screen similar to the one shown to the right may appear. It says "Press F1 to Run SETUP". It's that easy. Just press F1 or whatever key is mentioned to enter BIOS setup. The key varies according to motherboard manufacturer.
What if there isn't any screen like the one pictured here? Then you have to resort to trial and error. When you start the computer keep tapping F1. If that doesn't work try F2, Del, Esc, or F10. Or if you have your motherboard or computer manual just check what it says.

What we're interested in right now is to change the boot order. Again you can check your manual. You'll get this advice a lot on computer and tech forums. And often it isn't phrased so nicely. Enter the various menus (be careful not to change anything yet, there'll be time for experiments later) until you find something similar to the screen on the right. This is the boot order. Now you can change it to whatever you need it to be. If you to boot from a CD make the CD drive the first device. If you want to boot from the operating system installed on your computer make the hard drive the first. After you're done, find the menu item to save changes and exit.
More detailed how-to at about.com.

A question or instruction often given is "Can you boot into safe mode?" or "Boot into safe mode and then...". Well that's easy. When the computer starts just keep tapping F8. You should see the screen on the right. Move the arrow keys to select Safe Mode and press Enter.
For Last Known Good select that and press Enter.
Tutorial for different Windows versions at bleepingcomputer.com. Scroll down to skip the ads.

An ISO image is like a snapshot of a CD or DVD (or other drive). Instead of having multiple files and folders, all the data and structure is contained in a single file. When burning discs the information is extracted to recreate an exact replica.
Paraphrased from these Wikipedia articles:
Disk Image
ISO Image
A common mistake is to burn the ISO file itself onto the disc, instead of creating the CD from the image. Make sure to select the option in your burner software that says "Burn Image" or something similar.
Here's how to do it with Nero Smart Start, which comes free with some CD/DVD-RW drives: Insert the blank disc. Start the Nero software. Click Copy and Backup. Click Burn Image. Follow the instructions. You're done!

So you've decided to try out Linux and downloaded a live CD of Ubuntu or Mandriva, or maybe even Puppy if you have an older machine. You follow the instructions above and burn the CD, enter the BIOS, change the boot order, save changes and reboot! The CD won't work, grrr!!!
Let's assume that you didn't make the mistake of burning the ISO image as a file and that there's nothing wrong with your computer. There are two possibilities, you got a bad download or made a bad burn. There's an easy way to find out: check the hash value. A hash value is a string of characters that serves to verify the integrity of data. In other words if hash values don't match then the data has been changed or otherwise been corrupted. Two of the most common types are MD5 and SHA1.
Puppy Linux hash value is right there on the download page, where it says MD5 Checksum. Here are the Ubuntu MD5 hash values. Mandriva's MD5 hash value is on the download page as well.
There are lots of freeware downloads of programs that can check hash values. Just remember to only download from sites you trust and always check for viruses and spyware. What you need to do is get the MD5sum of your download and compare it against the correct value. Some programs will do this automatically. If it's different you need to download the ISO again. If it matches then your download is good and you need to check if your burned disc matches. You can't do that directly, you have to create an ISO file from the disc and then check the hash value. If both your download and disc ISO match the correct hash value, try burning at a slower speed.

How to open a command prompt
When asking for computer advice on the Internet you may be asked to "Open a command prompt and..." What's a command prompt? It's the white C:\> on the black text in a little box. If you remember DOS you know what that is, it shows you which directory you're in and it's where you type commands. Type commands? Are you serious?
Ok, how do I get to this "command prompt"? Simple. Hold down the Windows key and press "R". In the box that appears type "cmd" and press Enter. There! Or, you could click Start->Run then type "cmd" and press Enter. Or you could click Start->All Programs->Accessories->Command Prompt. But in some configurations it's not there.
I hear it's even easier in Vista. Click Start, type "cmd", press Enter. But I don't have Vista.

How to find your IP address
When troubleshooting network connectivity issues you will often be asked to find your IP address, Physical or MAC address, whether you have dynamic (DHCP) addressing enabled, and your DNS servers. At the command prompt (discussed above) just type "ipconfig /all" and all that information will be displayed. The MAC address is the Physical address. It's that simple.

How to change your IP address
You need to change your IP address, or change it from static to dynamic. Or change your DNS servers because the defaults aren't working. That's easy. Get to Control Panel (Start->Control Panel) then double-click Network Connections (Classic View) or click Network and Internet Connections then Network Connections (Category View). Right-click on the Local Area Connection and click Properties. Click on Internet Protocol (TCP/IP) then click Properties. On the window that appears you can either set your PC to obtain a dynamic (automatic) IP address or you can set a static one and set the subnet mask and default gateway (router's local IP address). You can also set DNS servers if the defaults given by your ISP aren't working.

More to come!

Your operating system won't start and you have important files on your hard drive. You read somewhere that you can access the drive by connecting it to other computer, either through the SATA or IDE ports, or through an external USB enclosure. You connect the hard drive to another computer, log-in as administrator, and try to access the file or folder. Access Denied. What, but I'm the administrator?!
You need to take ownership before you can access the files. Here are the steps:
1. If you are running Windows XP Home, start the computer in Safe Mode.
2. Log-in to an account with Administrator privileges.
3. If you are using Windows XP Professional, disable Simple File Sharing.
3.1 Open My Computer
3.2 Click on Tools then Folder Options.
3.3 Click the View Tab
3.4 In the Advanced Settings section, clear the Use simple file sharing (Recommended) check box. Click OK.
4. Right-click the folder which contains the files you need to access and then click Properties.
5. Click on the Security tab.
6. Click Advanced then click on the Owner tab.
7. In the Name list click the Administrators group then click on the "Replace owner on subcontainers and objects" check box.
8. Click OK then click Yes when the following message appears:
You do not have permission to read the contents of directory folder name. Do you want to replace the directory permissions with permissions granting you Full Control?
9. Click OK
Congratulations, you can now access the folder and its contents!

Sources:
Microsoft Help and Support: How to take ownership of a file or a folder in Windows XP
Microsoft Help and Support: How to disable simple file sharing and set permissions on a shared folder in Windows XP

Here are two articles on how to do it in Vista, these are not Microsoft sites:
vista4beginners.com
nirmaltv.com

Your XP computer frequently reboots. Chances are your system is encountering serious errors. Someone on a forum has asked you to post the contents of the BSOD (Blue Screen of Death!) but it flashes so fast you can't read it. The solution is to disable the automatic reboots. Right-click My Computer, click Properties, then click the Advanced tab. Clear the check box that says Automatically restart then click OK until you've exited all the various windows. Restart the computer (Ironic isn't it?). Now when your computer BSODs you can read it and troubleshoot it yourself (see my other lens) or get help on the Internet.

Identifying hardware components is of course a very important step in troubleshooting computer problems. A complete list should come with your computer's manual or if you had it built or built it yourself you should have a list of parts. If these are unavailable you can download programs that will show you useful information about your hardware.

CPU-Z - Great little program that will tell you all about your processor, motherboard, and memory. no need to install. Just unzip the files and run the .exe. To remove simply delete the files.

GPU-Z - Just download and run it to see information about your Nvidia or ATI graphics cards.

Common default router IP addresses are:
192.168.0.1
192.168.1.1
192.168.2.1
192.168.1.2
10.0.0.1
192.168.1.254
Type the address in your browser's address bar to access the router configuration page. You will then be asked to supply a username and password. Some common pairs are:
admin - admin
admin - 1234
admin -
Sometimes you will need to restore the router's default settings. Some routers require the power to be turned off, some don't. The manual is the best resource for instructions. There should be a small pinhole labeled RESET on the back of the router. Insert a pin or paperclip and press the small button inside. Keep it pressed for 10 seconds or until the lights on the router go out. The router will restart itself. Some routers require that the power be off when the button is pressed. The power is then turned on with the button pressed. Please check the manual or contact the manufacturer if you are unsure.

1. Search the FAQs and forum topics. Your question may already have been answered. This is common courtesy. No one wants to be rude to a newbie, but no one likes answering a well known question a thousand times either.
2. Read the forum rules and follow them.
3. Please don't post in leet-speak. Make an effort to spell words correctly and write grammatically correct sentences.
4. Give details about your problem. Post the relevant computer specs, the steps you've tried, and the symptoms of the problem.
5. Don't expect an answer within the first few minutes of your posting. Don't expect others to treat solving your problem as their highest priority in life. Be polite.
6. Share what you've learned.

When computer performance is sluggish and/or a malware infection is suspected it is useful to view the running processes. You can do this on Windows XP by invoking Task Manager with the Ctrl-Alt-Del key combination. Task Manager will show you the processes and how much CPU time and memory they are using. A much more powerful and useful program is Process Explorer. Process Explorer does everything Task Manager plus a lot more. It shows parent-child process relationships and highlight processes that have just started or ended. It can also display the processes' software publisher and whether or not they have a verified digital signature. It can also tell you which programs have a certain file or directory open. You can set the system to start Process Explorer instead of Task Manager when Ctrl-Alt-Del is pressed.

Here are some useful programs to help you diagnose computer problems:

Memory Diagnostics:
Memtest86
Memtest86+
Windows Memory Diagnostic

Hard Drive Tools:
SEATools (Seagate)
Drive Fitness Test (IBM and Hitachi)
ES-Tool (Samsung)

Bootable Images:
Ultimate Boot CD
UBCD for Windows (not affiliated with the original UBCD)

These are informal definitions intended to help computer newbies. The definitions used here are only intended to aid understanding and are not technically strict.

BIOS - Basic Input/Output System. This is the software that first runs when PCs are powered on. The BIOS identifies and prepares hardware before handing control to the operating system.

Boot - Start the computer, from BIOS to the Operating System.

Checksum or hash - A string of alphanumeric characters computed from digital data. It is used to determine if the data has been altered or corrupted.

Command prompt - A prompt where the user can type in commands to be executed by the computer. The prompt also displays messages returned by the system which are the results of the commands typed in.

Disk image or ISO image - A single file detailing the entire contents and structure of a disk. An ISO is a disk image that follows the format specified by the Inernatioal Standards Organization.

IP address - A set of numbers that uniquely identifies a computer on the network. A static address is assigned manually and does not change every time the computer starts. A dynamic address is assigned at every startup and may or may not change.

MAC Address - Also known as machine or physical address. This is a string of numbers and letters that uniquely identify network devices. Each network device manufactured (routers, network adapters, etc.) is assigned a MAC address at the factory.