Update: The card was defective and has been replaced with a new one. Now the computer is solid as a rock *fingers crossed*
I am at my wit's end here and hope you guys can help me out.
I built a new computer and installed Vista 64bit in December and have since been having nothing but trouble when playing older games like Rome: Total War and Company of Heroes, both purchased through Steam (I'm catching up on games my old system couldn't play)
After playing for any amount of time the computer will lock up in any of the following ways:
a) The image first getting scrambled and then the screen just shows weird colored lines. At this point the computer either automatically reboots, goes to a blue screen (sometimes also scrambled) before rebooting, or I have to to a hard reset.
b) Screen suddenly only shows the weird colored lines. Hard reset the only escape.
c) Screen goes to standby "no signal" mode. Hard reset the only escape.
In all cases the music will either continue in the background for a short time, or loop for a short time.
Windows Vista Home Premium x64
Gigabyte EP45C-DS3R motherboard
Intel Core2 Duo E8400 @ 3.00GHz (no overclocking going on here)
Force3D ATI Radeon HD 4850 (Catalyst 8.12)
Realtek High Definition Audio (on-board audio)
Edited for correct name of PSU: Seasonic S12 Energy Plus SS-650HT 650W
500GB Samsung Spinpoint HD502LJ (part of the F1 line AFAIK)
Also running Avast!
What I've tried:
Tried all versions of Catalyst from 8.7 - 8.12. I was getting the same lockups in Portal and HL2: Ep1 until I downgraded from 8.10 to 8.9.
Tried disabling virus protection
Disabled UAC and Aero
Updated motherboard BIOS
Tried to mess around with underclocking my card through the catalyst control center. It is now set to the defaults with GPU@625MHz and Memory@993Mhz (AFAIK these are the defaults). Weirdly enough, since installing 8.12 the control center is reporting my "Current Values" at 500MHz and 750MHz, the lowest possible settings.
Please help me out
The problem is either Vista or my video card, and I don't think I can find out unless I try formatting and installing XP again. That would be a huge pain as I really like Vista and am not sure where my old XP disk is (partly the reason why I purchased Vista). Also a friend of mine has been playing Company of Heroes on his Vista64, HD4850 system without any troubles, a fact that bugs me to no end.
Edit: I have played hours and hours of Left 4 Dead without any lockups. This problem seems to only happen with older games.