The HP 50g's FILER (left-shift APPS; it's labeled "FILES" on the keyboard) is your best friend after Try To Recover Memory leaves you with renamed directories. The FILER lets you easily rename directories, reorder directories, and even move them to different subdirectories. Its use is pretty intuitive, but details about using the FILER can be found in the HP 50g User's Guide.
Disclaimer: I don't work for HP. I'm just another happy HP calculator user.