Uuumm..i dont know, you could do a repair, but I dont think it would be possible because it needs to get rid of all the information, try running the setup within windows.
When it comes to the part where it shows the partitions, just install windows on the same partition. (the files only get deleted if u delete the partition) Then all of the files will be there but u will still need to reinstall all of the programs.
If I were you I would backup my files and documents and anything you want to keep and wipe the drive, reformat and reinstall windows. It'll be much better for you that way. It'll be a nice clean installation with no spyware and such and it will make your pc a lot faster. You should be doing regular backups anyway so it shouldn't be a big deal.