Computer crashes with looping sound

I forgot to mention that I have run memtest and found no errors in my RAM.

I don't get blue screens, it just locks up and forces me to shut it down manually.

When I run the computer on a piece of cardboard out of the case it ran fine, so I'm guessing it could be the case. What could be causing it?

I don't think there are any loose parts, but I am not using an I/O shield, because I lost the one that came with my mobo

The temperatures are fine, GPU going to around 70 in load, 40 idle, and CPU going to around 50 load and 35-40 idle. My room is carpeted. could that be an issue?

You know what I'm thinking...and I've used a lot of ultra power supplies, I like them, some guys don't, but they've been decent for me. However, my question for you is what is your airflow like near your power supply?

You say it's happening within 10-15 minutes of booting the machine? It sounds like a temp issue though you say temps are fine, because it's like a hard lockup? My theory is maybe the power supply is overheating. I have had this issue before with ultras. Decent units, but the fix I've found is easy. If you don't have one there already, what I've done is get a high flow case fan(I use an 80 mm, but 120 may be better), but get a high flow case fan, and mount it directly underneath your power supply to pull a cool stream of air under the power supply.

I realize there is probably a fan inside the power supply to cool it, but I've found that after I put a fan under my power supplies to pull cool air under the unit, apparently that helps exhaust extra heat, and I rarely, if ever get those lockups. That's first thing to check, because if that does work for you, should be at most like a 10 dollar fix, and especially with it being a 1000 watt unit, that puppy's gotta be generating some heat.

@CefVil - Thanks for the help. Yes, I use Win 7 x64.
@ohiou_grad_06 - I'll try the PSU fix.
@kikireeki - I'm using Patriot RAM, 1333 MHz DDR3. I've tried running with both sticks separately and the problem persists.

It's quite strange. I put a piece of cardboard under the case and now it is not freezing. I wonder if it is because of carpet static?

You could hit your case with a live wire and it wouldnt affect the PSU, the computer case, supports for the motherboard, and copper core of the motherboard are all connected to the PSU casing which is directly connected to ground. The exterior metal casing of any electrical object is grounded to prevent it from shocking you. There is no way static you pick up from your carpet before going to use the computer will affect it unless you carefully open up the case with rubber glove on and intentionally shock an IC.

I am having the exact same problem, with a laptop though, It seems that i can run the laptop without issue while it idles, but as soon as i enter a game or run any remotely strenuous pragramme it crashes, with the same sound loop explained. Some older games (-2001) can still run after the computer has crashed, with a noticeable drop in performance, but the sound continues to loop. As soon as you try terminating the game or try to load something new in the game it seems to get stuck.

Thanks, any help or suggestions that follow will be well received

Ive followed your link, and it looks promising, but i'm not sure what a fair value is to enter, I have no experience in this.

You say it's Patriot DDR3? And looping sound/crashes. Up your memory voltage. I always run Patriots and they absolutely always need a memory voltage increase. Happened on my Q8200, happened on my i5 build and happened on my Dragon and Leo builds. Some folks will cry foul but bump the voltage to 1.70 and if that's not stable pump it up to 1.75. As long as you stay under 1.8V you'll be OK. I know the usual wisdom with DDR3 is never go above 1.65V but in this case, it's OK.

I used the ELK 1333 Kit with the 9-9-9-24 timings for my i5 build (and I grandfathered those over from my Q8200 build!) and 1.725V is what it took to get these stable. Memtest won't find any issues even with the voltage being low, just FYI. I barked up that tree before realizing it was a power issue. Give it a whirl, you got nothing to lose (the JEDEC standard for DDR3 is the device must withstand 1.975V before experiencing any permanent failures) and Patriots follow those standards as do most big memory manufactures.

Another example: I use Patriot gamer memory (1600, 7-7-7-20) and it says on the stick that it's rated for 1.7V (thats above the traditional 1.65V limit) and I had to actually pump it up to 1.785V to get it stable. And even the tech support person said it was fine and won't void the warranty.

So give it a shot and run Prime95 BLEND and see what happens!