Swapped drive into new computer, now can't access My Docs

My friend's motherboard crashed so I offered to put his drive in my computer and burn his files to CD. The hard drive installed fine in my unit, and I can access virtually all the files except for the "My Documents" files for any of the users. If I try to access any of those types of files in XP or the Command Line I get an "Access Denied" error. I am sure this is just some sort of security feature, but now that the drive will no longer start in the original machine how can I get to these files? Both computers are Windows XP, and I can get the passwords if I need to. Any help would be very much appreciated.

-Chris