If you can't access the network try these possible solutions:
-Try to disable your firewall.It can block you to access the network.
-Make sure your account is set to have the permission to access the shared folder.
-Enable Netbios over TCP/IP.
-Try to use the Guest account.
-Run ipconfig /all and see what is the Node Type.It should be the same as the other computers in the network
You can find other useful information here:
http://support.microsoft.com/?kbid=913628