If you've lost the password for a Office 2000, then the only way to attempt a possible recovery is with the help of an application that was designed to recover password from these file types.
Luckily for you, there are plenty of these applications already created. You can browse the database of Software Informer to look for these applications. I have narrowed down the results to this search query. Use the following link then pick one application. Load the office file and try a recovery operation.
Search results: http://software.informer.com/search/office+2000+recovery