Things you can try:
1. Download, burn and boot from an antivirus CD to do that check you want.
2. See if windows-key + E runs Explorer. If so, you might be able to run your antivirus from there.
Kees
I was trying to boot up my computer in safe mode to run an AV program; however, when I booted up the computer I just get a purple screen with 3 buttons I can click: in the lower left hand corner is a button with a 3/4 circle and two arrows (when I click it the following options come up: narrator, magnifier, on-screen keyboard, high contrast, sticky keys, filter keys), in the bottom right hand corner is a button to change between keyboard languages and the power button to restart or shut down the computer. I can't get to the desktop and it keeps restarting to this screen. I've tried Shift + F8 upon startup but it never works. I have windows 8. When I when to system configuration I clicked the third option under safe mode (I think something with diagnose in it). I also changed normal start-up to diagnose start-up. Sort of confusing to try and explain this problem....

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