Spontaneous reassignment of alt-f4 to alt

[Wombat Pete]

Help! Windows 7 Ultimate, lenovo W520
I think this happened when I was maximizing a skype window by double clicking on the title bar.
An nview message window popped up - first time ever, and I can't reproduce it) and said that something wasn't doable... not sure what it said...
Possible as a result of that, alt now functions as alt-f4. If I'm on the desktop, it asks whether I want to restart the computer. If I'm in firefix, it tries to close it. alt-tab is unusable, and so forth.
Any ideas?
Thanks in advance!

 

[TrainableMan]

My first guess is a damaged keyboard, either the alt or F4 key. Try plugging in a USB keyboard and see if the issue can be duplicated on the different keyboard.

 

[Wombat Pete]

I would have thought so to, but I replaced the keyboard, and - no change.

 

[TrainableMan]

The problem is your laptop keyboard may still be triggering an F4.

I suggest you download and install Keytweak and try disabling the F4 key completely; obviously this won't fix your problems but it will show whether your F4 key is the problem.

 

[Wombat Pete]

I'll try doing that with a registry fix, you approve? It's an easy fix, I think.
I've already tried reassigning left-alt to left-alt, but it didn't help. Let me assign F4 to nothing and see whether THAT helps!