I got called in by next door neighbour whose daughter had managed to trash her hard drive. I put in a spare, and installed Win7RC1. It took about 15 minutes from start to finish - she was very impressed. It took another couple of hours to install the other software, set it up, and copy in her stuff from backups, though.
She's very happy, and looking for the best price for a "release" version of Win 7 come the day.
Compared with the XP Media Center Edition on there before, it's a major improvement.