What is the operating system installed ?
Did you have / Do you currently have any other security software in the PC ?
Do you received any alerts in the computer while going online .
How is the computer connected to internet ? DSL/Wireless/Cable
Got windows xp, windows standard security, no alerts when going online and cable connected. Funny, because yesterday i had another update and pc at risk again!
This frequent Your PC is at risk alert might pop up , if McAfee security center is nt uptodate or not receive the updates that should have been pending . As far as I understand , your situation should be the one as above . So , please run the McAfee virtual technician from here : http://mvt.mcafee.com which is an automated tool designed to solve almost half the issues with the product .