(This is really pretty deeply technical and I’m not going into a long explanation about it. If you understand what I’m talking about, fine. If not, don’t worry about it.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser\Parameters]
“IsDomainMaster”=”FALSE”
Also, the WebClient service (used with WebDAV to browse and share files via IE) can slow browsing of Network Neighborhood. Turn it off by stopping the WebClient service and see if it impacts on your operation.