Program Files Clean Up

I was looking through some of my program files and there is alot of stuff. That I don't use or have uninstalled that is still there. My question what can I safely delete that won't mess up my computer. Here are some of them uder Cocument and Settings Floder Application Settings There is a Spyware Terminator that is there that I don't use.
Document an Settings Folder Desktop there is Old AVG Spyhunter and Spyterminator folders I don't use these.
Then
C://Program Files all of the following things have been deleted from my computer or I don't use and the stuff is still there. Like
AVG
Big Kahuma Reef
IPOD
ITunes
Kaplan
Spyware Terminator
Trend Micro
Webroot.
And a bunch more that I don't use or don't know what they are.

Can someone help me or explain what I can do to clean up the files.

Cynthia