There are 3 windows 7 running PCs in my house. I started the homegroup last week and when I connected my netbook to the homegroup, it could access the one that started the homegroup but the other PCs couldn't access its files and it is not even visible in homegroup for them. I don't know what the problem is but it didn't happen for the third PC I connected to the homegroup.

Have you run the Troubleshooter, which can be found on the main Homegroup page?

yes I did. no use for sure.

Hi Make sure that there is something that is configured to be Shared on the computer. Make sure that the Software Firewall on each computer allows free local traffic. If you use 3rd party Firewall On, Vista/XP Native Firewall should be Off, and the active Firewall has to adjusted to your Network IP numbers on what is some time called the Trusted Zone (consult your 3rd Party Firewall instructions General example, http://www.ezlan.net/faq#trusted Please Note that some 3rd party Software Firewalls keep blocking aspects of Local Traffic even it they are turned Off (disabled). If possible configure the Firewall correctly, or totally uninstall it to allow clean flow of local network traffic. Jack, MVP-Networking. EZLAN.NET

I suspect that on the problematic computer the security programs such as antivirus and firewall block the P2P communications. I suggest you temporary disable or uninstall these programs and check the result.Arthur Xie - MSFT