Windows 7

In most cases it can upgrade over top of your Vista software. What it will do is make a copy of your Vista system before attempting the update. Then, if it is unable to complete the upgrade for any reason, it will roll back to Vista. I have loaded Windows 7 on to two PCs. With one of them, it upgraded fine and on the other one, I had to format my PC and do a new install (after backing up my data files, that is). But that PC had been giving me a whole lot of trouble on Vista with a lot of crashes and blue screens of death. Since I loaded 7 on it, everything is a-okay.

I installed Windows 7 right over the top of Vista and it's been rock steady. Seriously, my PC hasn't crashed one single time. I think you'll be very happy with Win 7.

Installation of Windows 7 over Vista will keep everything you have etc. but installing it over XP will require a clean install - which means everything will be written over.

Also, you can go here, to the Windows 7 Upgrade Advisor to make sure your computer and system can handle it