New Build Problem

[CanadienDude]

Alright, well last night I built my first computer, no problems, everything seems to be on, booted up first try, updated the bios to use my e6750 cpu, installed windows and went to bed. got home after work today, been installing various software/devices/updates for the last 3 - 4 hours, everything running great after many restarts.
SO anyway, I finally get to installing my anti-virus, it installs, restarts, comes up no problem, activates it, runs cc cleaner, restarts one final time after uninstalling yahoo instant messneger, and now at the Windows XP loading screen the little blue bars going across seem fine, then they just slow down and almost stop moving, forcing me to stay at that screen.
I reset the computer, booted in safe mode, came up fine, restarted, and the XP loading screen does that again.
Any suggestions as to what is going on?

Using XP
asus P5K
e6750 c2d
8800gts