I'd been away from my pc for a bit and when I returned there was a Sonic Installer on the screen telling me it couldn't install without the disc. I clicked cancel and it closed then came back up, started to run, and again told me it needed the disc. Couple of more tries and this continued. Tried to restart but that wouldn't work with the installer open.
Powered down and was able to get back to regular mode but Windows Installer came up, then the same Sonic Installer with the same results.
Just left it on the screen, followed all of your steps below, but again couldn't get restart to work with that installer on, so powered off. Turned it back on and went to safe mode to follow other steps. First went to look at the device manager and the Nvidia display adapter was gone, but I had a yellow question mark next to VGA controller. Details said it wasn't configured correctly, code 1. Sorry if that's perfectly normal, but I wasn't sure so thought I would mention it.
Ran Driver Cleaner Pro and it did remove some items. Emptied recycle bin and restarted. It loaded into regular mode but the Windows Installer then Sonic Installer came back up. Also received a pop up box that the computer had recovered from a serious error. Tried to close that several times and each time it came back up. Thought it might disappear if I sent the error report, but it came back. Sending the error report (which contained BC Code 7F) resulted in receiving a microsoft web page (I had by this point reconnected to the internet to go to nvidia and load the drivers). The microsoft web page said the error was due to a ram problem.
With Sonic Installer and Serious Error message still there, I loaded the 169.21 driver and during installation it said it couldn't load a component because the hardware acceleration was set to none. I remembered that we tried that last night and I guess didn't change it back. Headed off to go change it and received a blue screen before I could. Powered off and restarted and got a black screen. Powered off again and received a blue screen, so one more restart and came to safe mode.
In safe mode, I went and changed the hardware acceleration back to full and rechecked the "Enable write combining" checkbox. I have not restarted.
The system came with a nvidia 6 series. I had it a year, the upgraded to the 7600 I just took out 2 days ago. So it's always been nvidia. I am beyond willing to return the new 8600 and get something completely different, if that might help.
Thank you, Kristi