I have a person who asked me about antivirus software, so I suggested AVG. He installed it on his home computer and did a scan, where it found many virii. AVG prompted him to reboot, and now Windows won't start; he says it asks for a Windows 98 boot disk. He says that the computer should have Windows XP. I have never seen anything like this when I have used AVG; does anybody know what could be going on?