To find the default Server Repository location on Windows Server 2008 64 bit take a look in the registry for:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\PLESK\PSA Config\Config
If you cannot locate this try searching for
PSA Config or
DUMP_D.
The value for DUMP_D is likely to be something like:
C:\Program Files (x86)\Parallels\Plesk\Backup
Domain files, mail, databases are held individually in zip archives eg:
C:\Program Files (x86)\Parallels\Plesk\Backup\domains\undergroundgraphics.com
Looking for the Plesk Server Repository location for Windows 32bit or Linux 32/64 bit editions? Take a look at
How do I change the default Plesk Backup Repository location?