I almost always download the latest correct driver from nVidia, but last week I was lazy!
Windows update (Win7 32bit) presented one optional update, a January release for my nvidia GeForce 9600GT graphics card from Galaxy.
I checked the update and since the last time the computer went to sleep, the system has not been able to detect my PCIe graphics card at all!
I generally use Sleep rather then Shut down, so that WMC can wake up the PC for pre-scheduled recordings.
I've been googling away, and found many people with this problem, all appeared in the last month.
I dug out a VGA cable and plugged the onboard nvidia 6500 graphics output into the VGA socket on the monitor and was able to get up and running on basic graphics at least.
First I tried a System Restore, no good. Then I used Acronis (tool like drive image or ghost) to restore back to my last full C-Drive image taken just before xmas, this did not work either.
I downloaded the very latest nvidia GeForce 9600 drivers, no help.
The Windows Device Manager is detecting my PCIe Compro twin tuner, but not the PCIe graphics card.
I tried another PCIe graphics card (an older MSI 8600), same problem (I know this card works).
Next I tried disconnecting all power connectors, swapping my two 1GB RAM sticks, changing the 3V coin battery, resetting BIOS to defaults. I've been advised in the passed not to upgrade the bios on a DELL C521 as people have had killed their mother board, in any case it is only one revision 1.1.10 behind the latest 1.1.11.
I've verified the volts are still there on the PCIe external power connector, but then the MSI 8600 unit does not require any external power. I running out of ideas!
I don't beleive in coincidences, I doubt very much that a hardware component has died on the very first occasion I let Microsoft update my nvidia driver!
Its like some peice of flash memory has been set in a mode that has completely killed off running a PCIe card.
I remembered having a blank screen problem a couple of years ago on Vista, and swapping in the original ATI 1300 card got things going again, such that the nVidia card also worked when I swapped that back in (can't explain how this fixed things).
I finally found the old ATI card again, but even that won't work now.
I've also tried going back to the original DELL 280W PSU, keeping with original ATI PICe card, but still no joy on the PCIe graphics.
So I'm giving up. I'll leave it a few months before buying a new base unit or incase something comes up.