Well, The cd and dvd use two seperate lasers ( I am fairly sure ) so it is possible that your 'cd' laser is dying. You could also try cleaning the drive with canned air.

Aside from that, try finding a cd you can boot with. Windows may not be detecting the cd properly, but raw hardware may be able to. This would tell us to focus our efforts on windows, or the hardware.

Gluck - let us know.

Bipper