Cannot Boot PC – RPC Interrupted

I have a friend that has a PC with Windows XP Home Edition. It has been working fine until recently. When he tries to boot the computer he receives an error message stating RPC was interrupted and is shutting down. Then the computer reboots and he gets the same error message. This continues over and over and he never has been able to boot his computer. All he uses the computer for is Internet through a cable modem. Is there a way to fix this problem? If so, please give solution in detail as I will have to send it to him.

Thank you in advance for any help.