Windows 7 can't set up a home group on this computer.

Normally, a home group is automatically created when you set up a computer running this version of Windows, but you will be prevented from creating a home group if:
already exists on the network Family group. If a family group already exists, you will be asked to join the family group.
Homegroups are available for all versions of Windows 7. In Windows 7 Starter Edition and Windows 7 Home Basic, you can join a family group, but you cannot create a family group.
You may not be connected to the network. To connect to a wireless network, perform the following steps:
Click the network icon in the notification area of ​​the taskbar, click the network you want to connect to, and then click “Connect”. You may be asked to enter a network security key.
After connecting to the network, if there is a family group on the network, you can join the family group.
Your network location may not be set to “Family”. The family group runs only on the home network. To change the network location, perform the following steps:
1. Open the "Network and Sharing Center" by clicking the Start button and then clicking “Control Panel”. In the search box, type network, and then click "Network & Sharing Center".
2. Click on "Work Network" or "Public Network" and click on "Home Network".

Network and Sharing Center
If you are on a domain network and your system administrator may have completely turned off the family group, you will not be able to join the family group.
One or more of the required services are not running. “Peer-to-peer network grouping” and “family group provider” services must be running. Here are the steps to check:
1. Open the “Administrative Tools> by clicking the Start button and then clicking Control Panel. In the search box, type the management tool and click “Administrative Tools”.
2. Double-click “service”. • If you are prompted for an administrator password or for confirmation, type the password or provide confirmation.
3. In the "Status" column, the "Peer-to-Peer Networking" column and the "Family Group Provider" service should see the words "Started". If you don't see the word, double-click the name of the service and click “Start”.