Click with right mouse button on the .pvd file and choose menu entry "properties". On the upcoming popup window, the second tab should be something like security. Set the authorizations for the .pvd database accordingly and you should be able to access the file again.
The access rights settings on the database file prevent PVD from reading the file. Go to "file properties -> security" and define proper access rights. This is often cause when you move a database file from one windows installation to another...
I lost the hard drive on my laptop. Fortunately I am pretty careful about keeping back-ups on a removable drive. I installed my new drive and reinstalled my Windows 7 from the original disc. I restored my PVD folder from the backup drive but when I tried to launch the program I got a bunch of errors about missing files. I downloaded and installed the PVD program from the web again. Now it complains it can't open the database because of errors 24 and 37. I even tried restoring .bak file and it wouldn't use that either. I hate to lose the 300+ movies in the database. The program seems to open fine after complaining about the database.