Doesn't play dvds or doesn't read dvds? There is an important difference in those 2.
I'm going to assume you meant it can't read dvds. If that is the case, if you have a bootable DVD, such as a Windows install dvd, try to boot from that. That will tell you if it is a hardware issue or software issue.
DVD and CD use different lasers, occationally one or the other will die leaving you with a drive that only does one of the two. So that may have happened here.