This was very effective!
I had the exact error as described by the OP, DVD-RW appeared correctly in BIOS, however Vista did not show it in "My Computer" and it had the lovely Exclamation mark in the Device Mgr. Being a System device it had no special drivers to load... so don't waste your time dl'ing new ones.
I did the fix as mentioned to the two lines of registry (after making a b/u), simply deleting the contents of those two REG_MULTI_SZ entries and then a reboot...
Voila! The device shows up in My Comp and loaded a CD.
One caveat, my drive is a TS-H652H <-- not an M as in OP. hopefully that helps even more
I just wanted to make this post to asure searchers out there that this solution is viable given same pre-conditions.