Sorry to hear the Documents are still missing.
Let's try another option.
Well, I think you will have to restore Vista using Restore Center. To do this, click Start in the Start Search write backup and restore, then select Backup And Restore Center. Click Repair Windows Using System Restore, in the System Restore window select "Choose a different restore point" and click Next. Try to select the restore point (the date) before your friends messed up your computer. Then confirm the restore point and click finish.
Your computer will reboot and step back in time. I think, this will help.