What did I do wrong with this build, if anything?

Sounds like a possibly heat issue. Have you monitored temps under load?

That's difficult. I attempted to do that with GTA IV, unfortunately when it crashed it required a reboot. Once the OS was back up I checked the GPU temp (roughly a minute later) and it was at 48C, hardly a dangerous temp. I'm a little skeptical about a heat issue though, as there are currently six fans running in this case and this 5670 runs less than 75 watts under full load, which should work out to less heat than a more power intensive card.

Ultimately though, its tough to check temps when your system crashes and at any rate how could Mass Effect be so demanding that it would slow my system down to a crawl? Any other ideas, or suggestions on temperature monitoring?

Could be software, too. Make sure you have all the proper drivers installed, reinstall them if you want (I probably would).

The other thing is like purplerat said, heat. Sounds like this is your first build, make sure you have the CPU heatsink on properly. The 5670 should be fine on heat, unless the heatsink got slightly disconnected in transit.

So, my checklist would go:
Check temps under 3mark06 or something. Check CPU under Prime95 or some variation thereof. If CPU is above 55-60 degrees at load re-apply thermal paste + HSF. If GPU is too hot, take it out and make sure the heatsink has good contact against the GPU itself. Check your wiring, too. Poor cable management can bring tons of fans to nothing.

Reinstall graphics drivers.

If you unlocked/overclocked your CPU, undo that, too.

Thanks for the advice, some things helped.

Reinstalled chipset and graphics drivers.

prime95 cycled three times and CPU never got over 53C. couldn't complete testing on 3dmark6, first two tries crashed to desktop almost instantly, third try image was so pixelated I stopped test.

My cable management is pretty clean, lots of air going through that case, and nothing is overclocked.

My guess at this point is bad video card. Your thoughts? And thanks again.

By the way, this is my second build.

That's certainly sounding like something weird is going on! Have you checked if there is an updated BIOS for your motherboard?

Beyond that, I'd try running IntelBurnTest to make sure your CPU isn't causing the problem (this will work your processor harder than any other game/application, so it's the ultimate CPU stress tester). I'd also download and burn a CD of Memtest86+ to check the RAM is OK. Assuming you pass both of those then I think you're right in pointing the finger at the graphics card, but the only real way to test that would be to borrow another graphics card from a friend to try, or RMA your one and get a replacement.

Good luck mate, sounds like you've got a lovely build there and once you've got it working properly it'll be great!  

Does the graphics card need PCIe power connectors (can't remember off-hand) and are they connected?

It's your ATI Catalyst Control Centre. I had the same problem trying to play games and blue ray dvds on windows xp 64 and windows 7 with my HD4870. Try upgrade to the newest version for your card or get the newest drivers, or maybe roll back to a previous version.

as others have said - it sounds like a graphics card / drivers problem
from what I've seen the 5670 doesn't have extra PCIe power connectors so it's probably not that (though worth double checking your particular card)

update all your drivers to latest and retry, if that doesn't work contact whoever sold you the graphics card and tell them you think it's faulty


just a side note - but why install 4gb of RAM and then install a 32-bit OS?

I second the memtest86+ too. Bad memory does weird things sometimes. If your motherboard has onboard video, hook up that instead of the card and see if everything runs smoothly. If it does, the card is the problem.

My games wouldn't play rite on HDMI until I got Driver Detective it found new drivers for my old video card and motherboard then I built a new computer with a 2.8 Quad Core and 4200 video I ran Driver Detective it found up dated drivers for my new motherboard with Driver Detective or some other program you can't get any up graded drivers any more I use DVI to HDMI on a 32" flat screen once ATI Catalyst was downloaded my games worked on my old video card it was strange because by games worked on the VGA monitor it was when I went to HDMI I had a problem one problem could be the power supply if you are using 235w. to 350w. it has just enough power to run extra fans and every thing else check to see if the fans are running at top speed if they aren't your processor isn't running at top speed ether therefore your processor is over heating with my old computer before I went to more wattage output I had stalling on my games thats why when I built my new computer I installed a 650w power supply to start with you can't have to much power it's when you skimp on power is when you have problems