Help to retreive documents.

I have a Compaq presario 2500 40gig,i reinstalled windows xp professional after that. i couldn’t find my documents,pictures,music and programs in instaled. But in the Harddrive it show that i have free space of on 7gig space and other in use but i can’t find my stuff. Please i need help. i have checked the hidden files but i can’t find my stuffs.