A computer running Windows 7 Starter can join a homegroup, but you can't use it to create a homegroup.
Computers running Windows Starter cannot connect to a domain. Computers on your home network should be part of a workgroup instead.
Network bridging. If your computer is running Windows Starter, you cannot create a network bridge to join two or more networks together. However, a computer running Windows Starter can communicate with computers on a different network if someone on another computer has created a bridge between the networks.