Can't insert CD

I am visiting my parents in US and brought the data I need on CD's.
Sometimes the CD drive on their computer works fine, but sometimes the
computer does not recognize the CD drive (it fails to appear with the
other drives on My Computer).

Symptoms:
Cannot insert or eject CD---'shelf' doesn't come out when you press the
button.
Green CD light is on as though there is a CD inside.

Note:
When the player is funtioning OK, the CD drive appears in My Computer
even when there is no CD in the slot, and I believe the little green
light by the CD slot/shelf came on only when a CD was inserted.

Quick help would be greatly appreciated, as I can't access any of my
data...:-(...!

If I need to do something in Safe Mode, please tell me how to enter Safe
Mode. Please assume minimal knowledge on my part---need full directions...

Thanks for the help!
Janet