cdrw/dvd stopped reading cdrw's, has trouble with dvd's

I have an HP Pavilion ZE5170 with XP Pro SP2, and recently I found that
my CDRW/DVD is having problems. Unfortunately I installed a lot of
software before noticing the problem and can't pinpoint what could have
caused it.

I believe the drive itself works because it worked when I bought the
computer (used) both to write to CDRW's and to play DVD's, before I
installed a lot of software, couple of weeks ago.

I did notice that enabling UDMA-66 seemed to cause the drive problems,
and disabling it helped. But now after installing a DVD player I found
that it has a lot of trouble playing DVD's, a few seconds will play, the
player will pause, the drive will make lots of noise (I'm guessing the
head is jumping around looking for the track).

Is it possible that the drive was physically damaged by enabling UDMA-66?

Also, removing the drive from the hardware section of the control panel,
then rebooting and letting windows re-install it didn't help.

Any suggestions about how I can try to get this working again?

Thanks,
Mike