The fact that some of your software is still working means one of two things:
1. You performed a "factory reset" using the restoration disk from your system's manufacturer, or
2. You performed a "repair" install with a standard XP CD and these programs don't seem to mind.
iTunes version 4 was released in 2004, if you never updated it then I'd say that option 1 is likely. If, however, you had a later version installed before you reinstalled, then I'd say that option 2 is likely.
If option 2 is what's happened, then all your data is likely still there. Just run a search for the files using the built-in search function.
If option 1 is the case, however, your data may not be recoverable. Depending on how thorough, if any, a disk format was performed by the factory reset procedure, your files may be recoverable by using an undelete utility like Recuva
This is all speculation, though. Any additional info you can provide would be useful.