Bruno,
sorry bud!  :/ I couldn't go back and change the text colour, sigh.

Reposting the important bits for ya :)

A) downloading the latest drivers for Nvidia.
For 64 Bit Vista and an 8600GT card it's version 186.18 as of this day I post this thread. They change every few weeks
get right ones for YOUR system and card.

B) download "Driver Sweeper"
http://downloads.guru3d.com/Guru3D---Driver-Sweeper-(Setup)_d1655.html
This is used to clean up drivers left behind, as after many months/years, drivers can get left behind in your system, causing problems.

C) Back up anything you need to, just in case. As this is a serious endeavour I hope you back stuff up.

D) This next bit is an optional, but maybe an issue for you.- Check the version/date of nvlddmkm.sys which you'll find in Windows/System32/ folder, and write it down. Mouse hovering over it, should give you details in VIsta, maybe right click in XP? 

•  Because after doing installs (see below) it SHOULD update to the version you have installed, in this case verison 186.18 for Vista 64 bit as of this date of posting. 
•  If it doesn't update, that page I linked above has info on how to change it. basically, you rename the file, go to your Nvidia folder, copy the   nvlddmkm.sy_   file to that windows/system32/drivers folder, and use CMD command line prompt, which is a DOS window, in Administrator mode (you MUST have UAC off for this to work), and copy and paste this command in: EXPAND.EXE nvlddmkm.sy_ nvlddmkm.sys
• it will sort of unzip the correct file. CMD can be run by typing CMD into the START , SEARCH box in Vista.
• For those not familar with DOS commands, the command: <strong><span style="font-family:'Times New Roman';">CD..</span></strong>  will take you back up a directory, you want to get all the way to the top of C: drive by the way, so hit CD.. a few times if need, and a command like: CD C:windowsSystem32drivers will take you from the root of C: drive to the one you need
• Issue here is for a FEW people, that specific file is not being updated correctly when you install new drivers, leaving an old version behind.
   

E) Go to Control Panel, Programs and Features (or Add/Remove programs in XP)
Uninstall the Nvidia drivers

F) Reboot your PC, and before Vista/XP starts up, go into SAFE MODE, that's usually by hitting the F8 key on your PC. Some versions it's F5 or the Shift key, please check.

g) When in Safe Mode, use Driver Sweeper to clean out the Nvidia DISPLAY drivers, note that ONLY the Display drivers. It gives you clear neat choices to make.
If you wrongly wipe out your Nvidia disk controller drivers yer in deep poop! 

H) Reboot your PC

I) Start Windows normally. Install the previously dowloaded, most recent Nvidia drivers.
Reboot again.

"I'd rather be a Fool who believes in Dragons, Than a King who believes in Nothing!" www.silverblades-suitcase.com
Free tutorials, Vue & Bryce materials, Bryce Skies, models, D&D items, stories.
Tutorials on Poser imports to Vue/Bryce, Postwork, Vue rendering/lighting, etc etc!