I have successfully moved databases from one directory to another by just dragging and dropping in Windows Explorer as well as using xcopy. I find both of these ways a lot faster than using procopy. the databases aren't multi volume though, they are just single files (along with all of the necessary other files that is).
How are you trying to start your database back up again? Are you using a .pf file on your _mprosrv.exe command line? If you are you you need to change the path that is specified in the pf file as it won't be valid anymore (cos you have moved the db).
If that doesn't help, try and pro into it and see if it can at least still be opened.
Have you also tried looking in the log file, there might be some errrors in there that might give you a clue.
HTH,
James.