The Workstation service creates and maintains client network connections to remote servers. If this service is stopped access to network resources such as file shares will be unavailable.
A service can stop for many reasons, including:
The service was stopped by an Administrator.
The service encountered an exception that stopped the service.
The service was improperly configured, which prevented it from starting.
The service was prevented from starting because the user account assigned to the service could not be authenticated.
The service can be restarted using the Services snap-in which can be accessed through the Computer Management console task:
Start Computer Management Console