DVD not working after failed SP1 install

6 days ago I had a Compaq notebook (6720s) that was working OK, although USB
functionality was pretty random.

Then I tried to install Vista SP1 as offered by Windows Update. The install
failed. 2 different System Restore points also failed.... Terrific.

Now the system no longer shows DVD drive in My Computer or Computer
Management, but
it shows in Device Manager as not working, no drivers.

I've tried the Upper and Lower Filters fix that everyone seems to suggest.
No good.

The DVD drive is a Matshita UJ-860H. It spins and tries to read media so
it's not dead.

Help needed please anyone?

Andy