When adopting a Windows 7 machine as a file server, it may run out of resources with these entries in the Event Log:

Event Id 2017 The server was unable to allocate from the system nonpaged pool because the server reached the configured limit for nonpaged pool allocations.

Client computers will get messages about read-only or resource not available.

The following changes will resolve this:

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\LargeSystemCache = 1

HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\Size = 3

Then reboot the machine.