Windows frozen, Ctrl+Alt+Del doesn't work

My 64-bit Windows 7 often freezes up and Ctrl+Alt+Del doesn't work. Please help.

Do these freezes happen at random times or only when you're doing some specific computer task?

At a minimum I'd run a full scan for malware using your installed AV of choice. I'd follow up with a second scan using the free and highly recommended Malwarebytes.

https://www.malwarebytes.org/products/

I'd also check to see if you have any damaged or corrupt system files by running a System File Checker scan from an elevated command prompt (Option Two, this tutorial.) If any problems are detected run the scan three more times and reboot your computer after each scan.

SFC /SCANNOW Command - System File Checker

I'd also suggest going through this troubleshooting tutorial prepared by one of the Forum experts. Follow the steps in the order given and don't skip any.

Troubleshooting Steps for Windows 7

Dear Marsmimar,

Thank you very much for trying to help me. I tried the recommendations you'd advised, unfortunately the problem still exists. The problem appeared after upgrading the Windows from 32 to 64 bit. Generally the problem appears when I'm on-line (Chrome or Firefox). I repaired the system by the installation CD, but there was no use.

I just formatted drive C and installed a new copy of 64-bit.

hi are all the driver installed any error in device manager?

Yes, all the drivers are installed and there is no error in the Device manager.

Since this is a new install you might consider doing a repair install. Perhaps there was a glitch or hiccup during the initial install.

Repair Install

I did it twice, no use. Additional info: I noticed that usually Windows freezes up when I try to watch a video online.