If your files have been moved or copied to a new drive, all paths (links) to the correct location of the media files have been lost in the catalog. Each location is known not only via the drive letter, but also via the serial number of the drive.
That's why the only simple and recommended way to transfer media to a new drive is to use the backup and restore process in the Organizer. You can choose the destination drive and the restore process takes the new drive identifier into account. Another advantage is that the catalog will be converted automatically to a newer PSE version.
You could try the option to 'reconnect missing files' but that's not a practical choice for a big catalog even though PSE11 is better in that respect.
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Moving Files to New Drives and Computers
Change a Drive’s Volume Serial Number
The psedbtool utility won't work for versions 9 and above, but the explanations may help you.