Andy,
Have you tried the built-in "Compress & Repair" under Tools? There are
several freeware tools available (and I'd have to look them up to tell you
what they are) but I've found that the Access tools did about as good as the
freeware tools I've found. Certainly not an expert at databases but be sure
you work on a copy just in case it gets mangled when trying to revive the
database.
Bob S.