I am using Office 2003 with Windows XP.

I recently moved all my data files to a flash disk. When I did so, I
reassigned my various Office components (Word, Excel, Powerpoint) to that new
drive (Identified as Drive H, using the Options dialogue box. All worked
fine.

When I restarted my computer, the drive designation was changed from H to O.
I reassigned Word and Powerpoint to Disk O; but Excel will not allow me to
do anything on the Options dialogue box, indicating it can't find Disk H.

How do I get past this so I can reassign Excel to Disk O?