Three words: Backup, Backup, BACKUP!

It's very difficult for anyone to feel sorry for you when you don't backup these supposedly important files of yours.

At this point, my initial thoughts about your situation is that you got hit by some nasty malware and your system is pretty well screwed. With a Linux LiveCD and a USB flash drive, you might be able to copy off the files before you have to format the system. Depends on how big they are. You may want to consider an external hard drive over a flash drive.

You might also be able to limp along for a short time by installing XP Pro over top Media Center. Just long enough to copy off some files, but I wouldn't go thinking that's a permanent solution.

In any case, let this be a lesson on the importance of regular backups. ALWAYS, ALWAYS, ALWAYS back up important data. The more important it is, the more redundant backups you should have. Very few techs will ever feel sorry for you if you tell them your sob story and it doesn't include some catastrophic event like a tornado or hurricane hitting your house and blowing away your computer AND backups, not to mention ripping out the vault with your safety deposit box, containing off-site backups of your most important data, and depositing it at the bottom of a lake or ocean. If something like that happens, we'll feel sorry for you. Come to us saying you have no backups, and you'll be lucky if we don't say something along the lines of, "I told you so!"