I also messed up before I reinstall the data. I was checking the hard drives to make sure the connections are OK and when I was putting back the cables, I put my backup drive as primary. So when I was installing XP, it actually recognize my previous backup drive as C: and then erase all the data on it. Now my hope is that actual original C: drive does not have any physical damage so I can rescue the data from there somehow.
Any help is greatly appreciated! I am really desperate now since I lost my backup drive due to my own stupidity.