I just cleaned out all the old nVidia graphics files in Safe Mode, and then re-installed the 185.85 drivers for the graphics card (8800 GT) and also removed and reinstalled the nVidia System Tools software again (6.05), while in Safe Mode. Installation went much faster than in normal mode, but nVidia Control Panel still won't run, with the same error message. Since the System Tools also use the Control Panel as their shell, obviously they don't run either. The error occurs both in Safe Mode and normal mode.

So, something is interfering with, or blocking, operation of the nVidia Control Panel software modules. Maybe also affecting graphics drivers, but not sure. The task now is to find out why my system is blocking and others don't have the problem.

Note: I did have nHancer installed, but not running. This program overides some of the nVidia Control Panel settings for a graphic card, but that software has been uninstalled prior to the re-install of drivers.

I am about ready to consider a re-install of Windows Vista 64. I only have the original (no SP1 or SP2) version, so a re-install will be a long and arduous affair. Not looking forward to that prospect at all, so if we can find another way to discover the culprit, it sure would be nice.

Thanks to all for your support and assistance.

Doug

I cleaned the registry with CCcleaner with no improvement, and, yes, I did try just loading the graphic drivers alone first. My primary concern is the nVidia control panel since it manages the setup and features of the video driver, and if it is broken, there is no telling what the driver is doing or how it is set up. This isn't a problem with normal generic computing, but with games, simulations, graphics heavy applications, etc. it can make a very big difference.

If others are having the same problem, I'd like to know if any of them have found a solution, or if anyone has determined that some event caused the problem (like the installation of SP2?).

Hey, thanks loads! That one worked like a champ, but was a really grueling series of tasks to accomplish.

I followed the 31 step process, exactly, using Driver Cleaner.net as the cleaning agent, as recommended. I used CCleaner to verify that the registry was in good shape before installing the nVidia drivers. It found one additional nVidia item that needed to be removed. The multiple passes of the cleaner after successive reboots was necessary, each time catching more and more items to remove. The register removals took quite a few searches to find all the items needing removed. I don't recommend this method for anyone not understanding how regedit works and what damage can be done if you screw up. The process outlined on the nVidia forum assumes a thorough knowledge of Windows files, the registry, and how they work.

Bottom line, control panel now works, and I was able to load the latest nForce drivers for my motherboard at the same time.

Thanks again for finding this process. Its a winner!

Doug
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For reference, here is the method, extracted from the nVidia Forum, member Luttiano: [bracketed items are mine]
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It turns out that driver installations have to be done "while" in safe-mode or else they won't bypass native driver support that vista offers. This occurs even if you had update drivers turned off. So, here's how I fixed my issue for all of it.

Normal Mode :

Turned off automatic driver updates (set to "never" was confirmed) [after done, reset to "ask before installing"]
Uninstalled Nvidia motherboard drivers
Uninstalled Nvidia display drivers
Ran DC.net cleaner [Driver Cleaner.NET]
--Cleaned nvidia
--Cleaned nvidia control panel
Rebooted

Safe Mode :
Ran DC.net cleaner
--Cleaned Nvidia
--Cleaned Nvidia Control Panel
Rebooted

Safe Mode :
Ran DC.net cleaner
--Cleaned Nvidia
--Cleaned Nvidia Control Panel
--Do not reboot at this time.

[for the following reg changes, use search to find all occurences]

Opened Regedit and removed the nvidia CPL registry keys
Deleted the NVCP*.* files from windows\system32
Deleted any NVC file that housed a description of Nvidia Control Panel from windows\system32 [pass mouse over file and read "description"]
Used CleanMyPc Registry cleaner [or CCleaner] and fixed all registry issues
Rebooted

Safe Mode :
Installed Nvidia Motherboard Drivers [latest]
Installed Nvidia Display Drivers [latest]
[installed nVidia System Tools]
Rebooted

Normal Mode :

Display works 100%
Control Panel works 100%
Multiple Monitor Support works 100%
Problems Fixed!

Thank you for your wonderful support. By the way, now, for the first time, I can now get the Performance Monitor section of the Control Panel to come up (aka: nTune). Haven't seen that for a long time. I may even try SLI again, since I was never able to get it flying in Vista 64 before. I tried out the graphics engine on the new RailWorks train simulator, a very graphics intensive and touchy piece of software, and it worked perfectly. Prior to the work we just did, it would not run, most likely because it was relying on generic drivers instead of the proper nVidia drivers.

Best regards,

Doug