Infected computer Help me out!

My father is running Vista and currently he is in Georgia. Suddenly I got an email from my father with some unexpected subject so I tried to reach him and found that he didn’t email me anything. He has lost the control on his computer and unexpectedly getting a pop-up message. I tried to use about 10 antivirus programs. I don’t know that is it browser hijacker or adware. Please help me out from this problem.