i agree with meese. Unless, when you reinstalled windows, you told it to format the drive or delete the winnt directory. When i reinstalled windows XP Pro last week, i told it to use the existing winnt folder on my C: drive and it said it was going to delete all the info in that folder.
If that is the case, you will have to go out and purchase a file recovery program. Do not install any more software until you have attempted to recover your files. A friend of mine reformatted his laptop a couple of times before reinstalling XP and then ran a file recovery program and retrieved all of his files. I appologize but i do not recall the name of the program of the software vendor, but it was pretty well know.