Thanks for your referral... but the program recommeded (RegCure) didn't work.
HOWEVER, I have fixed my problem--it was definitely the dirver. Here are the steps I took:
1. I went to the site recommended by Butch and downloaded the program RegCure and ran it. It found ~850 "issues" with my installation during the scan. When I went to have RegCure clean up the "issues", I was rudely informed that, while it can and did identify issues in several areas on my machine, the freeware version only addressed problems in two (2!) areas. I only had a few issues in one of the "free" areas and none in the other. So... I went back to the site and paid US$29.95 for the full package and had it clean up the mess. The result? NO CHANGE, but I now have a super clean registry; which can't be all bad.
2. Then later in the day from the fog of my brain, I remembered a screen flash that I saw that indicated where the nVidia drivers were being stored after downloading and extracting from nVivia--C:\NVIDIA. So, looking in there, I found folders named Win2k and WinXP. Looking in both I found still more folders named 169.21 (Win2k); 180.48, 181.22 and 182.06 (WinXP). Checking the dates of the folders' creation, I found the 169.21 had been created in March of 2008--about the time that I built the box. So...
3. I installed the drivers from that folder and all is well. I have been running rFactor for a few hours this evening and it looks like I'm back to a stable video system. Now all I have to do is tweak it a bit.
iotgl72, I hope yyou can search your folders and find the original (or, at least, an older set of drivers so you can get back to your prior state.