PC Access has prompted you for a drive letter, and you have entered something other than a letter corresponding to a diskette drive on your computer. If your computer has a diskette drive, you may enter A, A:, or A:\. If your computer has a second diskette drive (and you want to insert a diskette into that drive for PC Access to read), you may enter B, B:, or B:\.
If you are certain you have entered a drive letter corresponding to a diskette drive your computer actually has, follow the instructions for an Internal Error.