If all you want is access to two different subnets, you can specify multiple static IPs in the TCP/IP | Advanced settings of the network adapter. If you have DHCP at both, it's easy to get a new address - at most it's an "ipconfig /release" "ipconfig /renew" when you move the box to the new location. If they are mixed (one DHCP network, one statically assigned) then have an address reserved for you on the DHCP network to prevent conflicts.
Then make sure you have added your workstation as a member of both your home and office domains. This will add an extra option for the domain you want (or "local computer") in the logon options pull-down menu.
Caveats: If you are on W2K server and you don't want to route between the networks (if you happen to be on both at the same time, although it doesn't sound like it since "office" and "home" indicate two geographically separated locations :-) ) then make sure to disable or uninstall routing. If you are on W2K pro, you're all right.
Hope that helps -