People who have owned their current computer for a longer time than some others may not know that not everything comes installed on your computer before it goes to the place you bought it from (unless you buy a Dell, and they charge you to put the stuff on anyhow).

Microsoft Office - you only get a 60 day trial version. If you have kids, or are buying the computer to use for school...you need to pick the software up in some form or another.

Virus Protection - You will more than likely end up with a trial version of Norton. Norton sucks. The software that you get from your internet provider is decent, if you don't use your computer that much. If you're a heavy user, you'll want to pick up something that is at least virus protection and spyware protection, if not more. Trend Micro PC Cillin is a great program, and it has a couple different levels. Webroot Spysweeper is a good spyware program by itself, as well.

General Software - Well, there's enough usable software on the computer once you get rid of all the advertisements, but you probably want to download iTunes, Winamp, Firefox, a bittorrent client, Nero for burning dvds/cds, and some other basic stuff.