Odd computer slowdowns

[TheWongizzle]

Hi
lately my computer has had odd lagging problems within games/applications that requires the computer to use accelerated graphics. Its usually very sporadic lag, it comes and goes and usually my whole game slows down.
Oblivion lags after 3-4 minutes
Company of Heroes lags sporadically.
Warcraft 3 causes my entire computer to crash at random times.
Sometimes after my computer crashes or just restarting, the startup screen just looks like a bunch of pixelated lines.
sometimes it starts up to be a bunch of horizontal white and black lines.
This never used to happen to my computer, it just started happening.
i used to be able to play oblivion without a hitch, and now it lags all over the place and sometimes it crashes.
i dont know whats wrong. The computer refuses to draw certain textures sometimes and the lag becomes unbearable.

Once my computer crashed, i saw a very quick blue screen that i wasnt able to catch anything. then i heard some beeps from my motherboard. Thats only happened once though. and it crashed from Warcraft 3.

Here are some system specs (taken from DxDiagnostic)

Operating System: Windows XP Professional x64 Edition (5.2, Build 3790) Service Pack 1 (3790.srv03_sp1_gdr.060315-1609)
Language: English (Regional Setting: English)
System Manufacturer: System manufacturer
System Model: System Product Name
BIOS: Default System BIOS
Processor: AMD Athlon(tm) 64 Processor 4000+, ~2.5GHz
Memory: 2048MB RAM
Page File: 457MB used, 2996MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 9.0c (4.09.0000.0904)
Card name: NVIDIA GeForce 6800 Series GPU
Manufacturer: NVIDIA
Chip type: GeForce 6800 GT

Oh, and i have an Asus A8N-E motherboard

please help.

 

[j12]

i would guess its a heat problem either in your cpu or gpu.