Set Default Printer based on different Locations (Networks)
Windows 7 has a new feature called location-aware printing that switches the default printer automatically based on the network you are connected to.
Only available on laptops or portable computers that run premium editions of Windows 7.
Devices and Printers
Click on one installed Printer
Click on Manage Default Printer in Menu bar
You can now set the default printer for each network (locations) you connect to