(Obviously change the command to reflect the location of your Office 2000 install file).
Using the ALLUSERS=1 command changes the install mode so that it installs Office 2000 on a per machine basis instead of a per user basis. This seems like the most likely way to install Office 2000 so it doesn’t keep asking you for the CD.
One article suggested copying the contents of the CD to a network location and installing from there. I know that this doesn’t work, but it may work in conjunction with the ALLUSERS=1 switch?
You should use the msiexec /a command to do an Administrative install of Office 2000. I’m not sure if it’s required to do this to copy the files, which you then install from the network location, or if that’s your install done.