if it sounds like it's crunching the disc, it's normal.
This happens to me at work when I'm at a meeting or something. A real showstopper.I hate it when I'm at my local college library and I insert or remove a CD/DVD...all that noise crunching it makes in the middle of such silence!
The nice thing about those manual loading drives is you can keep a disc in them and it just stays there. My macbook won't let me - it ejects the disk from the superdive whenever I shut down.