In Excel 2003 (installed more than 3 years on my machine), the File Menu has
suddenly become extremely slow to open - 10 to 20 seconds - while all the
other Menu Bar menus are quite snappy. In other Office apps the File Menu is
also snappy.

Only changes to my system in the last few days have been C drive defrag.

Editing the File Menu, Office Repair and System Restore to a point before
the Menu problem have had no effect, as well as disconnecting network drives.

Any ideas where I might insert a fix for this?