You just need to give yourself rights to the folder...
Log into the new OS as an administrator.
Open up My computer.
Click on Tools > Folder Options > View, and uncheck "Use simple file sharing" at the bottom of the list.
Right-click on his old user folder (\Documents and Settings\[username]), then select Properties.
Click on the Security Tab.
Click on Add, Type the name of his account, click on OK
Give him Full Control...
Click on Advanced, and edit the entry you added for him...there will be a drop-down to select "Apply onto this folder, subfolders, and files"
Click on OK and it'll probably tick away for a bit re-applying the security to all the folders/files under his old user folder.