Try to boot the Windows 2000 CD. If you can't boot that CD, then the machine needs repairs.
I run Win 2K SP4 on a Dell Optiplex GX110. The PC has ceased to read from either CD drive. I have an internal CD-ROM drive (Samsung) and an external CD-RW drive (Yamaha) connected via USB. The Device Manager indicates both drives are working normally, but when a disc is inserted Windows returns the message "Drive is not accessible; incorrect function". It doesn't matter what kind of disc is inserted or what type of file I'm trying to access. I attempted to uninstall and reinstall the external drive, without success.
Any suggestions and advice would be most welcome.