AO - Just so happens I am currently re-commissioning a Dell Optiplex 745 which my son had upgraded with an AMD graphics card.
After re-installing Win7/64 (using generic drivers), I noticed that the text on the second display for some web sites (notably the New York Times) was absolutely 'orrible* - pixillating to the extent that it was unreadable in places.
Re-installed drivers using AMD Catalyst Control Centre** (about four hours ago), and now everything is fine.
Thereby proving that Microsoft's choice of drivers is sometimes somewhat dodgy and you sometimes you really do have to go the extra mile and install the OEM drivers.
* Actually is was far far worse than 'orrible, it was fricking truly totally and utterly 'orrible!
** Why can't they simply call it "AMD Driver Update"? Pillocks!