I own a 400Mhz AMD K6-2a Multimedia HP Pavillion PC with a CD reader. One day, the CD reader showed a blipping light whenever a CD is inserted and have no access to its content. I see the D: drive icon in My PC and the System applet does not report any failure (in fact I can eject the CD from the CD player). Is my CD reader damaged?

From your description it sounds like it's broken. You could try cleaning it.

I would not trash that cd-rom without giving it a second try. I would check to make sure the IDE is plugged all the way into the controller on the motherboard and the back of the drive, as well as the Molex(the power plug) into the back of the drive. I often have more time than money, and it can be helpful to reinstall drivers for the drive, but often if it wont help. But you might get lucky, you just never know.

Drivers can literally disappear overnight, in fact, I once serviced a computer where the drivers had been completly deleted, most likely caused by bad sectors in a cluster.

Also, make sure the CMOS recognizes the presence of the drive. However, it is most likely a loose IDE.