I have been having issues with Lightroom 5.7 closing for no reason. The last time it asked me to ener seriel number, but I entered a previous number for Lightroom 3. I corrected this later, BUT I cannot access my A drive with all my photos, I seem to have lost the catalogue. Any suggestions please. Considering buying Creative Cloud - will this correct the problem?
Open LR and go to the File menu. Look for and click on Open Recent. How many catalog names are in there?
If more than one click on each one to open them until you find your real catalog file. LR will shut down and open using the catalog file you selected in the previous step.
Also the drive letter A is reserved for Floppy disks, and so is the letter B, so you can't have either an internal or external hard disk drive with that letter.
Buying a new version of LR won't correct the problem of your lost catalog. It also won't correct the problem of LR shutting down all of a sudden. That is more than likely a computer hardware problem that you must fix as soon as possible.
Lightroom cannot access the A: drive or the B: drive on Windows computers. Move the photos to some other drive.