Just about any windows application breaks down what its doing into a few dozen threads, its up to windows to assign a threads to a CPU, unless of course there are applications that are designed to use two CPU's, at that point you will actually notice a nice performance increase. Dual CPUs are really meant for server applications, like webservers, database servers, where there will be hundreds of new threads coming in and lots of old ones to kill. I dont really see the need for a dual CPU set up for Office 2000, unless maybe you have some very intense Excell calculations running on a Sh%*load of records.
If you want to get smooth Office 2000 work done on Win2k, this is a good setup:
800Mhz CPU or Higher (preferably 133 Mhz FSB)
Partitioned Drive, or better yet seperate drives, one for OS one for Applications.
256MB of Ram this gives Win2k room to work, 384 would be a tad better but more than that for office applications and you wont notice any improvement.