Hi,
Try to boot in safe mode and verify if the computer works fine without freezing. To boot to the desktop in safe mode keep tapping F8 key during restart. Once you see the option to boot in safe mode select it and press enter.
http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode
If the computer works fine in safe mode, you try to put the computer in clean boot state to make sure that third party applications are not causing this issue with computer performance.
To perform a clean boot, follow the steps below:
1. Click Start, type msconfig in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
2. On the General tab, click Selective Startup.
3. Under Selective Startup, click to clear the Load Startup Items check box.
4. Click the Services tab, click to select the Hide All Microsoft Services check box, and then click Disable All.
5. Click OK.
6. When you are prompted, click Restart.
7. After the computer starts, check if it works normally.
