I've been very happy with W7. I upgraded from Vista using an MS upgrade disk which was supplied to us free by the computer supplier (we bought a PC shortly before W7 was released). The upgrade went faultlessly, took about 90 minutes I think, and didn't mess with any of our data or settings. There were two points during the upgrade where nothing seemed to be happening for some time, but actually there was nothing wrong. The W7 upgrade has to match the Vista OS (e.g. Vista 64 bit needs W7 64 bit upgrade), as Mornington Crescent says.