It will be very difficult to recover much of anything useful off the system.
If you have a second computer then you might be able to do some recovery by
connecting the Hard Drive as slave to a second system and using a decent
recovery tool that can read NTFS as I assume you converted the file format
to NTFS during the clean install. Or if you have a second Hard Drive you
could remove the drive in question, attach the second drive a s Master and
install XP to it then connect the drive with lost data as slave. You see you
really need a second drive so you can recover lost data to. You can't
recover the data to the same drive it was lost on. Doing so will further
overwrite other files.
I've had some success with apps like Lost n Found from
www.symantec.com or
Windows based programs like iRecover
http://www.diydatarecovery.nl/