You can with an inexpensive add-in, but from memory I don't think the option is built in natively - I'm not in front of a PC with FrontPage 2000 nistalled and so I can't confirm 100%, but I certainly don't remember anything that does pop-out menus being a built-in feature.
There are a lot of third party products that can produce the necessary code which you can then insert into your FrontPage site by pasting the code in 'code/HTML view'.
This click here is one of many FrontPage add-in components that gives extra functionality to the parent prgram. There are lts more and a search in Google for this:
will lead to more options than you can deal with.