The BBC has a nice article about the pain of installing Vista - incredibly it sounds a lot like Linux on the desktop a few years ago (IE having to dig deep into the system to get things working). Its also rife with incompatibility and most machines will need a lot of upgrading to get those pretty windows.
In short - its going to cost you a lot of time and money.
Ironically modern distributions like Fedora, Ubuntu and Suse are a lot more ready for the desktop than that pile of junk and do the business with a lot less.
Now if only we could turn this into our advantage...