re: Uninstalling Vista
I wouldn't install any operating system that wasn't at least two or three years old. I'm just now debating moving up to Windows XP from Windows 2000.
Best bet, unfortunately, is to copy all your data files, and as many preferences as you can get away with, scrub the primary drive down to the bare metal, and reinstall your old system and applications from scratch. I have to do this anyway every few years.
There's a reason I keep all my data, even e-mail files, on a specific data-only hard drive, or at least a separate partition.