Actually the guides you can read on the internet (this site included) give a very bad advice. Never use driver cleaners, uninstall utilities and stuff like that unless you have an already broken system and that's your last chance. Thing is, these applications kill your system, that's why you can't update after using them.
Start out from a clean OS install, and next time you want to update the drivers, just install the new release on top of the old one. You system won't have trouble anymore.
CPU: AMD Phenom II X4 810 @ 3120MHz | RAM: Kingmax 2x2GB DDR2 800 @ 833MHz| MoBo: MSI K9A2 CF v1.0 (BIOS: 1.D)| GPU: Asus HD 6850 1024MB (DirectCu) @ 835/1135MHz | Display: L24FHD | PSU: PC Power & Cooling Silencer 750 Quad | OS: MS Windows 3.11 Pro x64