Strange, unresponsive Windows

I've been working with computers for a long time and I'm stumped. My problems started all of a sudden a couple of weeks ago. At least twice a day some program in Windows 7 Pro 64-bit will stop responding. I don't mean that the "Not Responding" window pops up--I mean that the program just sits there. Mouse clicks do nothing. Clicking the Start button does nothing. Pressing CTRL-ALT-DEL does nothing. There's never an error message; we have to do a hard reboot. I ran scans with MBAM, Spybot S&D, and Microsoft Security Essentials. They found a few usual tracking cookies, but no malware or trojans. I was gonna try a Windows restore, but I don't have any restore points from before this started. Windows is up to date, as are my video drivers. Now I haven't had this computer very long, only three months or so. I REALLY don't want to reinstall Windows. Can anyone suggest an approach to fix this problem?

 

Is it just one or more programs that stop responding?

 

I've had that happen to my 32 bit Win 7 desktop about 2 weeks ago.
I ended up having to hold in the power button to turn off the computer.
I have no idea what was going on but I had to shut down the computer a few times that way.

It hasn't happened lately.

Can you look in event viewer and perhaps see what is going on. Look at the times when this happen then when you control the computer again, scroll for that time period and see what is going on.