I cannot open a backup file of the catalog.

I always backup via LrC to the C-disk and copy the backup to the D-disk. I tried to open the backup from both disks but that made no difference. I made a new folder with the backup, but again, no success. What I have is:
(1) - [ ]New folder
(2) - [ ]My Lightroom-3-2-v13-3 (folder)
(3) - [ ]My Lightroom-3-2-v13-3.lrcat-data (folder)
(4) - [] My Lightroom-3-2-v13-3 (zipped file)
When I try to open/unzip (4) I get the message "Cannot find My Lightroom-3-2-v13-3.lrcat-data... Perhaps the files have been moved..."
When I click Continue I get the message that (2) is protected against writing and cannot be opened. (Incorrect authorisation?)
Recently I have changed my C-disk, so there has been some moving. But backups LrC made since then give exactly the same messages.

My message boxes are in Dutch. I try to give what seem to me the most relevant parts.

If you backed up via LrC, then the normal procedure is as follows:

• Copy the backup to a different folder
• In that folder, un-zip that catalog
• Double click on the un-zip catalog

Now about that lrcat-data file, it may or may not have been included in the backup. Is some AI masking was accomplished, then it should. If it is missing, you should get an error message stating as such, and you would click on continue, and LrC may recreate it.