Recently my parents needed to take their computer, a HP Pavilion a6528p PC with Windows Vista Home Premium, in for service after a Trojan "anti-virus" snuck onto it. The techs added McAfee Security Center and disabled Windows Defender. Everything seemed fine for the last three weeks.
However a few days ago my parents discovered that the USB ports aren't working properly. While the USB keyboard and external hard drive still work perfectly their camera and MP3 player are not able to interact with the system. Everything is getting power but the PC doesn't recognize them or even acknowledge they're present aside from the rare "Unknown device" message.
They had not plugged in the camera or MP3 player in this time period so it's likely been a problem since that point.
Can you help?
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It could be a security setting in McAfee causing the problem, check by disabling it temporarily and see if the devices work with it disabled.