Maybe a hardware problem?

I recently updated my desktop computer with a Nvidia GeForce 7600 GS (agp slot) and well we went to bestbuy (well geek squad) to upgrade it, they put a disk in and told us that one, we had a winlogonhook trojan and 2, our OS (windows XP) was "broken" but we've never ad ANY sort of problem with the OS, Now all of a sudden this trojan is acting up, and it screws up my computer enough to well, it froze up everytime i restarted it (i was in the process of removing it, and my internet kept giving out, and dls froze and stuff) so since it froze everytime on startup, i did a system recovery. Once it finished it would restart....and restart....and restart....and restart...and...and well i think you get the point... It goes to a black screen saying my video card and ram and stuff, to the HP Logo then it goes to a black screen, couple sec later it goes to the Microsoft load up screen, sits there about 20 sec, and then it goes to a black screen...my monitor turns like a brownish color(from green) and it like restarts it keeps doing this over and over and over..and i have NO clue why...Now i dont no if its my OS or if its something i did while i was trying to install my new video card, but this is just getting old...and ive tried removing the graphic card and doing a recovery, still no effect what so ever...So can anyone help me? and im dead serious when i say id love u...forever...=)
thanks all at Major geeks, ur all a big help =D

Specs:
512 gb ram
2.2 ghz
Amd anthlon xp 3200
default vid card is Nvidia GeForce MX 4
120 gb hard drive
OS=Window XP
and thats about it, thanks guys!

 

Double post.This is also in software section.