What is the problem ?

I have a PC, not in domain. It is in network through NIC to other computers.

It had 2 OS installed. Windows XP and Windows Vista. Some days earlier XP didn't work, it said "Reinstall the hal.dll file."I am working on this.Currently, this is not the issue. I am using Vista now. Vista works fine.

The problem is that from Vista, i cannot connect to other computers in the network when i try to connect from "RUN"(By typing IP in the run like \\192.168.1.170).The username and password asking dialog box prompts, but doesn't let me access the computer. But i can use the other computer by using Remote Desktop. The same user name and password works with Remote Desktop.What may be the cause ?