XPS 400 freezes

Ladies & Gentlemen, I need your help.  I am running an XPS 400 running XP Pro MCE (SP2) and these components:

2 Intel Celeron 2992 mhz processors

1gig memory

OYC523 motherboard

NVIDIA GeForce 6800 video adaptor

Dell 1905FP Monitor

100gb hard drive of which 47.1 gb are free

I did have an HP PSC 1110 all-in-one printer installed but it got to the point where it wouldn't print due to computer errors so i deleted the program a week ago.

My computer came from dell with XP installed and unfortunately, I don't have any hard discs with which to reinstall.

I normally use FireFox for internet surfing and like to play downloaded games.

About a month ago, my computer started freezing.  The screen would freeze and the sound would loop on the last sound made before the freeze occurred.  I have downloaded and run Malware AntiMalware and originally found some problems that have been fixed for a week now and found no problems when I ran it last night.  I have avast antivirus running full speed at this time as well.  I also have windows firewall active.  I also just ran CCleaner and it is fine and also have used System Mechanic and it shows no problems.  All of these programs are recently installed since the freezing occurred.

I cannot figure out why my computer continues to freeze.  SInce removing SP3 and getting rid of the problems with Malware, it doesn't freeze as often but still freezes.  I've tried adjusting accellerations both sound and hardware to no avail.  I've done a memory diagnostic and drive diagnostic at startup and both showed clear.

About a week ago, I left my computer off for several hours but accidently left my monitor on.  when I booted up the computer, it wouldn't boot up and i got two lights lit up on the front of the terminal (#'s 2&4) which I later found out was supposed to mean a potential problem with the graphics card.  I turned the monitor off, turned the computer off and turned it back on and everything has been fine with that issue since.

The freezing happens some with FireFox or IE, usually when playing games, but rarely when working with other applications.

I'm feeling lost and don't know what else to do.  Any advice would be greatly appreciated.

Oh, finally, in Event Viewer, I'm getting come Com+ system application errors and TCPIP security limit warning.