..you need to tell Windows 7 that you want to use the machine as a file server and that it should allocate resources accordingly.
Set the following registry key to ‘1′:
HKLMSYSTEMCurrentControlSetControlSession ManagerMemory ManagementLargeSystemCache
and set the following registry key to ‘3′:
After changing the two registry settings, I simply restarted the “Server” service in Windows 7 and now the sharing is working fine.