You don't need to change workgroups..you can still access any computer in any workgroup. Workgroups are only a visual layer in network places..they are not related to permissions or anything like that...you see people say "Computers MUST be in the same workgroup to access each other.". Not true at all. Same workgroup means they are simply in the same visual layer in network places. You can still kick up one level..then go across into another workgroup. Just means you have to double click 3 more times in network places.
Or..if you travel between them often...and don't want to navigate network places..just drag a shortcut to the share on other PCs to the desktop. That way you can immediately access their shares, not worry about navigating through the network.
So the laptop is in "Workgroup" at the office, and his home network is named "Home Wireless". There's a computer at his home, named "homeserver"..which has a shared folder called "stuff". Take his laptop home..click on start==>run...and type in \\homeserver, click on OK. Within a few seconds..explorer should open up showing the shares of homeserver. You'll see the folder named stuff. Drag a shortcut of it to his desktop. Now..whenever he goes home, he simple double clicks that shortcut..instead of drilling through network places.
Another method..right click network places..select search for computers..type in the name of the PC you wish to get to..it'll show up regardless of workgroup.
Or start==>run==> \\IP address of computer you wish to get to.
Or...take one of the networks and rename the workgroup on all the PCs.