Use a working computer with the same version and service pack level of Windows XP.
Copy the %SYSTEMROOT%\CSC directory contents from the old hard drive to the same location on the working computer.
On the working machine, open a command prompt.
Type csccmd /enable
Create a target directory, for example C:\Restore
Type csccmd /extract /target:C:\Restore /recurse
Your files will be extracted from their compresses offline files format back to their original format!