First of all, do you have a backup? If not, at least backup what you currently have immediately before analyzing, just in case you need to go back to your current DB for some reason.

The command line that is in the shortcut "Analyze VSS DB" on the Start menu is:
"C:\Program Files\Microsoft Visual Studio\COMMON\VSS\win32\ANALYZE.EXE" -x -v1 "C:\Program Files\Microsoft Visual Studio\Common\VSS\data"
Just replace
"C:\Program Files\Microsoft Visual Studio\COMMON\VSS\win32\ANALYZE.EXE" -x -v1 "C:\Program Files\Microsoft Visual Studio\Common\VSS\data"
with the path to your VSS DB's data directory.

Hope this helps.
-EM