Computer crashes and/or restarts in Portal and Steam

[The.Spiral]

Ok, I've spent a full day trying to figure this out with Steam Support and other forums, and the problem is still there.

So I bought the Orange Box yesterday, and I installed Portal first. While downloading, my computer randomly restarted. It happened two or three times. After finally completing the download/installation, I launch the game. I was able to play the whole fist map, but as soon as I saw the first "loading...", it crashed (without looping sounds). After a reboot, I tried again, and the same thing happened.

After reading a couple of threads on Steam Support, I found out that AVG has compatibility problems with Steam and Source games. Funny, because I was able to play 5 hours of HL2: EP1 without any problems whatsoever. Anyway, so I restarted my computer and made sure only Microsoft processes were running and I disabled the rest. Same thing. I changed my video drivers form the latest Omega to the latest Catalyst, but it didn't change anything.

So I uninstalled AVG, same thing. Oh, at one point I was able to pass though the first loading point, but I stopped to change VSync to On, and when I pressed ok it crashed... and when I tried to load my saved game in that map, my computer restarted. I even reinstalled Steam and Portal. Nothing changed...

Oh, my computer restarts whenever I "Verify Game Cache Files".

If you have any idea how to solve this problem, it would be much appreciated!

I haven't tried TF2 or EP2 yet, I'm going to try that tonight and see what happens...

Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2
System Model: 775Dual-VSTA
Processor: Intel(R) Core(TM)2 CPU 6300 @ 1.86GHz (2 CPUs)

Memory: 1024MB RAM
Page File: 685MB used, 4336MB available

Card name: ALL-IN-WONDER 9800 SERIES AGP 8x 128MB
DirectX Version: DirectX 9.0c (4.09.0000.0904)
Driver Version: 6.14.0010.6755 (English)

Sound: Realtek HD Audio output
Driver: Driver Version: 5.10.0000.5273 (English)

 

[Rapstah]

Your GPU is integrated, right? Would be bad if it didn't support DX9, but as it does it's just moderately bad. The random restarts when trying to fix the program sound violent, though, do a virus search.

 

[The.Spiral]

Thanks for the fast reply!

My GPU isn't integrated... I bought that videocard especially for HL2

Nothing was found with AVG... I'll reinstall another anti-virus and see what happens.

 

[Rapstah]

Oh, sorry, I mixed All-in-wonder up with a card I saw on a laptop, and that wasn't it.

 

[The.Spiral]

I installed Avast! and ran a virus scan before windows starts, it found on virus in the system restore directory and I deleted it.

I deactivated Avast! before launching Portal, I was able to go though the first map but my computer restarted exactly at the first loading point.

I really don't know what to do... is it a hardware problem?

 

[The.Spiral]

Update:
I downloaded and played Episode 2 and Team Forteress 2 without any problems whatsoever, but I still can't pass the first loading point in Portal without my computer to restart.

Any ideas?

 

[Rapstah]

If your computer has stopped restarting when you verify game caches, do that for Portal and report back.