Dvd drive reading problems?

What happened was the desktop crashed completely, I don't know what caused it, possibly films I downloaded from the internet. I cleared the partition and reinstalled xp. It seemed to be okay but now my dvd drives aren't working properly. They can all read dvd's but when I put a blank one in it shows as format raw, and 0 bytes used and 0 bytes available. I've been scouring the internet but can't find any answers, it may be something to do with "top and bottom layers" filters or something but I can't quite get my head around it. Any ideas?