Hi, I was using my PC (just using Firefox and Videopad Video Editor) and suddenly my screen turned into what looked like

a 'full screen' Internet Explorer screen (i.e. what it looks like when you press F11), and I can't close it, can't Alt-Tab to any other applications, can't CTRL-F4 to close it, and when I restarted my PC, as soon as I got into Windows 7 this dratted screen appeared again, and I can't do anything with my PC at all.

Pressing CTRL-F4 seems to close it for a split second, as I briefly see the desktop (for about a tenth of a second) and then this bloody screen reappears. I can't get Task Manager to appear either, it seems as if this screen overrides everything else on my system and takes precedence.

I have Windows 7 64 bit (legal) and have been using it for about eight months, with no problems like this, up to now. Is it a virus or something? Or an overactive program, trying to 'call home' or something?

Many thanks to both of you - I've rebooted in Safe Mode, and am typing this on my PC now, and am running Microsoft Security Essentials, and Malwarebytes, and scanning my whole PC. (Only about 3TB of data! Should be finished in a day or so).

price_th, how do I log in as admin? The only thing I have managed to do is to get into Safe Mode by pressing F8 on start up, I couldn't even access the Start button before (there was nothing on my screen except for the full screen Internet Explorer window, and no way to get rid of the wretched thing). Can I choose to log in as admin when I reach the password screen when Windows 7 is loading? I've never tried it so wasn't sure.

One further clue that might help - I think I had Excel open as well, just before the problem occurred, and now that I'm stuck in Safe Mode for the next day or so, while my 3TB of stuff is scanned for viruses/malware, I wanted to do some more work in Excel, but when I try to open it, it opens and has a dialogue box which says "Microsoft Office cannot verify the license for this application. A repair attempt failed or was cancelled by the user. The application will now shut down', and when I press 'OK' it shuts down.
It's a legal version which I installed (Office 2010) about two months ago, and have had no problems with it.
I thought that maybe the reason it wasn't working now was because I was in Safe Mode, but when I read the message more closely, it sounds like something went wrong with it, and it tried to repair itself. Is that possible?
Can I uninstall it and reinstall it while in Safe Mode?

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