Annoying problem with DVD drive not reading some Dvds

I recently bought command and conquer 3 for PC and its not working...
i know it has something to do with my dvd drive/drivers because i recently reformatted my computer. The game is on DVD-Rom, but it wont read it, i have Windows XP home. The drive reads CD-R, CD-RW and movie DVDs, but it wont read the game and now it wont read blank DVDs. My DVD drive is a HP DVD Writer 840b.I have no idea whats happened and any help would be greatly appreciated.

Avenue to explore:

http://support.microsoft.com/kb/321640/