Need Help Updating Video Card Driver

HELP! I've owned a computer for 3 years, but don't know the first thing about updating to a new Video Card Driver or re-installing the Driver that shipped with the card on the CD. My card is an Nvidia based card made by PNY technologies named Verto GeForce 4 MX 420 64mb sdram PCI. Yup, it's a PCI card. Got an old system. The manual that shipped with the card makes no mention of updating or re-installing drivers, and I've searched both Nvidia.com and PNY.com for info on updating or re-installing the drivers, and there is no mention of the procedure on those sites. I called PNY tech support, but they're only open during bussiness hours, and after being on hold for 30 minutes had to go back to work. Sent an electronic message 10 hours ago, and still no reply. The reason I want to update is that I had a Crash To Desktop after running a 3D game, and afterwards the video display seems blocky and pixelated, even though I'm at 1024x768 resolution. Could a CTD damage a video driver? I suspect I should re-install the old driver or update to a new one but don't have a clue how to do this. It would appear to be a state secret...Thanks for your help!

Thanks, Holy! Just a little nervous about the warnings I see here and there: Be sure old drivers are completely removed...Shouldn't I install the VGA Driver (I know that much), then re-boot and remove the old main video driver first? Comments, Anyone? Anyway, thanks very much for your reply.

OK then, guess that should work. Thanks for the link to Guru 3D, great site!