RE: dvd drive problem
hardware fault or if your lucky a dirty lens, you can buy a cleaning disc, it has a little brush on the disc and when you put it in the drive it whizzes round and cleans the lens.
Though if it doesnt recognise any disc all the time then I would put my money on it being faulty.
The fact the PC recognises it is nothing to do with it playing discs. Its certainly not a driver problem. This is right back at the barebones and is a hardware problem.