Duncan writes in with a hardware question
Q. Hi, My problem is that when I start my computer up and reach my log in page, my mouse works but as soon as I press my keyboard to type my password the whole system freezes. I have tried various keyboards but same result. I can’t login. Any help you could give would be amazing, thanks.
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Answer: Try booting into Safe Mode and choose Last Known Good Configuration. This will start your computer using the configuration that worked successfully last time you started your computer.
Or you can see if you can actually log into Windows from Safe Mode. If so then you can try a System Restore to put your computer back to a state before you started having this problem.
You can also edit your startup items using msconfig to make sure that there is nothing set to boot with your computer that shouldn't be. This could be causing your system to hang.