VACUUM locking for 21 hours and counting

Hi all,

context:

PostgreSQL 7.0.3
Database containing one table with ca. 500,000 records.  It's vacuumed
nightly, but normally doesn't change much.  The table is, arguably,
overindexed, but it took a lot to get acceptable performance on the
queries which it runs.

I delete 120,000 records from the big table.

I run VACUUM.

21 hours later, I'm still waiting for it to finish.

What on earth can I do?

Oh yes, I _did_ run a backup just before doing the DELETE, but would
really rather not have to restore that right now.

Thanks,

Hal