I had the same problem with a customers PC few weeks ago, installed some games from CD (retail kids games, not sure which one), and the next day, both DVD and CDRW are listed, but cant access either, this is on XP.
I wonder if theres some DLL libraries these games maker is using that conflicts with the OS or changes the registry. After spending almost a day crawling the registry and makeing/restore Ghost to test, I finally gave up, and installed a fresh copy of XP over the old one, then both the DVD and CDRW came back just like magic.
Sorry Ale, this may not be the answer you are looking for, but this is what I had to do to 'fix' the problem
Reading Harry's website, he had an article, read that Nero, if not uninstalled correctly, will give the same type of problem, but only under XP, so I really do think its the games that must have changed or corrupted something during their installation, just cant point a finger to it.