The chances are that the computer isn`t infected by a virus at all. Despite what you say Mcafee is a very good anitivirus program. What makes your friend think it is infected?
Most likely is that he`s picked up malware and I would agree that Mcafee isn`t particularly good at stopping these infect the computer, particularly if your friend has unsuspectingly clicked on a website link or e-mail attachment and "Invited" the program to install.
click here and download Malwarebytes Free Edition. Then click here and download the Portable Version of SAS.
I would run these even before removing Mcafee or installing another antivirus program. If it is malware the chances are that the malware infection will also prevent any updates of these programs anyway.