I have this ongoing issue with games that shouldn't be happening.
I have a 9600 GT graphics card, Duo Core Intell Processor, Plenty of memory 4 Gigs of RAM, Razer gaming keyboard and mouse, all the good stuff. The drivers are all updated.
I got this card a while ago and I always have this problem, any new game, such as Call of Duty 4, Fallout 3, or whatever (this applies to all games except for FarCry2 for some reason) will only run for a few minutes then crash to a black screen and keep playing the same sound over and over again very quickly. Its very strange, all older games work fine.
Any ideas on resolutions?

You running xp, vista or 7?

My first thought would be a driver problem, but since you said all your drivers are updated that probably isn't it (although you could try rolling back to a slightly older graphics card driver and see if that makes any difference). My other thought would be a RAM problem, as that can cause the kind of crashing you described and will most commonly show up with memory-intensive applications.

It's hard to give a definite answer without more information. The general stuff would be to check things such as refresh rate, search the Nvidia forums, and check the settings in the Nvidia control panel. Do you have the latest DirectX 10 for Vista and 9 XP/Visa Runtimes? If you could list your system specs it would be helpful. You could also try uninstalling the driver in safe mode, running driver sweeper and reinstalling the latest driver, although I don't know what that would do to your system. Thanks.

Oops, for got about that stuff.
Windows Vista Ultimate 32 bit
DX 10
Already reinstalled driver and disk defragged

Could it be the card tuning thing is all wonky? It happens to me all the time. When I mean tuning, I mean that driver program with the thing that lets you select the percentage of your card. Or I'm just pulling that out of my ass or something.

Try installing the Omega drivers http://www.omegadrivers.net/ or the NGO Optimized Driver http://www.ngohq.com/home.php?page=Files&go=cat&dwn_cat_id=10 or the DNA Drivers http://www.donotargue.com/list.php?c=dnanvidia Hopefully that may fix your problem.

Download Rivatuner, check your temps when you play the games, then post them here.

I'd be curious to know what sort of temps your CPU and graphics card are getting up to.

I'd be inclined to suspect a memory or overheating issue.
Vista includes a fantastic new architecture which should mean that faulty drivers will restart automatically. You'd also see a notification telling you that your drivers had restarted.
First, try looking at your control panel for "system reliability" or some such. It's been a while since I've used vista but there are some decent tools which will tell you if the OS has noticed something go wrong.
Secondly, you could try downloading memtest86, burn it to a CD, boot from it, and see if anything pops up.
I'm inclined to think it's a memory issue because you'd probably not notice it playing older games, which wouldn't use all of your memory. A fault in the high memory (3-4Gb) could stay unnoticed until you play the most intense games.
Thirdly, try and grab some temperature monitoring tools and then run some taxing applications, like prime95 for CPU or 3dmark for your video card. You'll probably get a good sense of what the problem is before too long.

My experience has been a heating or driver issue.
Check the vents are clean and not blocked by their environment.
A number of people are reporting issues with the 19x.xx series drivers, Nvidia has promised a fix, but people are reverting to 185.85 to get around them.
Aside from that, it could be any number of hardware or software issues, and we'll narrow it down over time.

Has it always done this? Is it a recent development?
Is the room the computer located in air-conditioned? Is it a desktop or laptop?
Full specs. Mobo, CPU, gfx card including manufacturer, Power Supply, RAM speeds (default and what you're running it at), fans, etc. Check the BIOS or use Sandra SiSoft or something if you don't know how to figure this out yourself.
Do you have Directx10 installed? No, really. Check again.
Were the drivers updated according to the latest drivers on the dell website? Or the latest version of the drivers for your card? Version #?
I agree with everyone else though. Probably a heat issue or drivers. If you haven't already, I'd put on the A/C. Also, if it's a laptop get a fan pad for underneath it.
Also,like dom said have you tried benchmarking it with 3dmark or something?

easy method to check whether heating is the problem
http://freestone-group.com/video-card-stability-test.htm
download and run it for half an hour. if it crashes there is something wrong with your gpu.
for cpu
http://majorgeeks.com/CPU_Stability_Test_d215.html
folding at home and other programs like that are also a good way to check CPU's performance (since the max out the output)

Heres my dxdiag information-
Vista Ultimate (6.0, Build 6001)
System Model: Dell DM061
BIOS: Pheonix ROM BIOS PLUS Version 1.10 2.4.0
Processor: Intel(R) Core(TM) 2 CPU 6400 @ 2.13GHz (2 CPUs) ~2.1GHz
Memory: 2558MB RAM
DX 10
Chip Type: GeFOrce 9600GT
DAC Type: Integrated RAMDAC
Approx Total Memory: 1523 MB
Display Mode: 1680 x 1050 (32 bit) (60Hz)
I'll try to get those heat measurements, but how do I do it?
We actually had a owner of a computer repair company come over (he's our friend) and he took a look around my computer. He thinks it could be a problem with vista hogging all the virtual memory, and since I can't allocate more to the card, its just crapping out if I pump up the graphics, so I'm going to try to lower to 16 Bit when I'm playing games to see if it helps. He said if this isn't it it may be a hardware issue, and since Best Buy screwed me out of my money already (we took it in to have it looked at when the card was still under warranty but they charged us $100 anyway) I should just go buy another of the same card, install it, then see if there is a change in performance. If so I'll just keep the new card and the other would be a bad experience, if I have the same problem Ill just return the card that I just bought.
Sorry if thats a bit confusing :)

My 2cents would be:
1. Test that memory with memtest 86+ for a few hours
2. Are you using on-board sound? try a sound card and see what happens
3. Downgrade to DX9 and see if the same issue happens
4. Don't use the video card drivers from the manufacturer, go to nvidia and grab them
5. Are you overclocking? if so, stop then test
6. Enter the BIOS and reset to defaults and test
Let us know what happens