Dvd rw drive not reading discs (DVD and CD)

Question

I am running Vista Home Basic on an Acer Aspire AST-180. I have an Hitachi DVD RW. I have owned this PC for just over a year and have been burning DVD's without issue. All of a sudden it has stopped recognizing and disc that I insert into the drive. A lot of the time it will also lock up the PC until I eject the disc as well. Help?