This is actually pretty common, because the drive has two different lasers in it - in infrared laser to read CDs and a red laser to read DVDs. It's pretty typical to play DVDs a lot more often than CDs, and so what happens is that the red laser eventually burns out while the IR laser is still working.
Since repairing the laser would be a lot more expensive than replacing the drive, it looks like you're going need to buy a new one.
Thanks, when I insert a CD, Windows XP recognizes it, but when I insert a DVD, windows sees it as "no disc" I hear the disc spinning and the drive trying to read it, but nothing happens. Gonna replace the drive then, does it matter if I get IDE or SATA?
Let me ask you on more thing, I happen to also own a Blu-ray/HD DVD combo in another PC. Now, blu ray plays back fine, but Im unable to play HD DVD. Windows Vista does recognize the disc as HD DVD, and even names the movie title correctly. Does that means that the drive is working correctly? Am I lacking the proper software to play it?