You can't, natively. It's one or the other. And you probably don't need to
do this at all anyway....you have need to change to a workgroup just to
access resources on it. You shouldn't play with your laptop's network
settings at all. Once you've logged in using your domain account (using
cached credentials), and have an IP address on the network in question, you
can map drives, use printers, whatnot, very easily - one way, in a command
line:
net use x: \\computername\sharename /user:computername\username <enter>
A Windows 2000 computer cannot simultaneously be joined to both a domain and
a workgroup. If the NetBIOS name of the domain and the workgroup are the
same, you may be able to achieve a unified browse list of domain and
workgroup machines.