Well ... what happens is that very often, only when I connect to internet, I get a window that says "is shutting down the system. Save all work in progress and log off. Will not lose any changes that have been saved. Been initiated by the NT AUTHORITY \ SYSTEM for the remaining time off: (1-min and goes down until it turns off)

Message
windows must restart now because the service Remote Procedure Call (RPC) terminated unexpectedly so after that my computer is restarted, and installed an antivirus and an anti-spy ware and found some things and removed but the problem persists, can you help?