If you need to re-do the os, then get a linux live CD and you can recover your data that way by copying it to a jump drive/burn it to a CD (with an external CD burner). Then re-do the OS and be happily on your way. Make sure you back up EVERYTHING! I know this works by experience too.
EDIT: I will have a good Linux Live CD with me if you want to use it. Just visit the TechnoKats pit and ask for Schnabel.