I have a powerbook 1400c/166 which is no longer recognizing the hot-swappable cd-rom. The floppy drive which used this port is working fine. I even bought another cd-rom (used, but guaranteed) and it is doing the same thing. Just spinning. Any answers?

Try reinstalling the CDROM extension. And check the electrical contact points both on the 1400 & the CD module(s) to see that they are clean and not bent, pushed in, or mangled.

Try putting your PB 1400 to sleep, remove CD ROM and wake up. Put to sleep again, insert CD ROM and wake up. This should help.

I have the same problem. The problem started after I increased the RAM and installed system 8.1. If I disabled the CD ROM extension in 8.1 and moved the old extension from 7.5 to the 8.1 extension manager and activated it would that work?

It generally is a bad idea to mix-and-match extensions from different versions of the MacOS - especially when they are from different major releases (7.x vs. 8.x vs. 9.x - not to be confused with OS X). I hate to suggest this because it is such a pain in the a** to do, but what I would do is a clean install of the OS. Boot off the CD ROM if you can. With the PB 1400 you MUST hold down the following keys BEFORE you see the happy Mac: Open-Apple, Option, Shift, and Delete. The CD ROM should spin and you should boot off the CD. It will be obvious that you are booting off the CD because of the noise. Then after performing the clean install, you can move over third-party system extensions from the Previous System folder to your new extensions folder. It is possible that you have software that conflicts with the 8.1 CD ROM driver.