See if any of these links help;
http://windows.microsoft.com/en-us/windows7/Why-can-t-I-connect-to-other-computers
This is from the 3rd link;
Password-protected sharing is on by default for computers in workgroups. When password-protected sharing is turned on, people using other computers on your network can't access your shared folders or printers unless they have a user account on your computer. There are two ways to turn on file or printer sharing:
Create identical user accounts on all computers in the workgroup (recommended). For more information, see Create a user account.
Turn off password-protected sharing. To turn off password-protected sharing, follow these steps:
1. Open Advanced sharing settings by clicking the Start button Picture of the Start button, and then clicking Control Panel. In the search box, type network, click Network and Sharing Center, and then, in the navigation pane, click Change advanced sharing settings.
2. Click the chevron Picture of the chevron icon to expand the current network profile.
3. Under Password protected sharing, click Turn off password protected sharing, and then click Save changes. Administrator permission required If you're prompted for an administrator password or confirmation, type the password or provide confirmation.