Thank you for posting the thread on Microsoft Community.
As per the description of the issue, after you upgraded Windows Vista to Windows 8 Pro your computer freezes.
Please provide me the following information.
1) Do you get any error when the computer freezes?
2) Have you installed any third party antivirus or security software on your computer?
3) Have you made any changes to your computer prior to this issue?
I would suggest you to please follow the method given here.
Method 1: Boot the computer in Safe mode with networking and then in Clean Boot.
Step 1: Boot the computer in Safe mode with networking.
With the Windows Startup Settings screen (formerly advanced boot options) you can start Windows in different advanced troubleshooting modes so you can find and fix problems on your PC. In previous versions of Windows, you could get to this screen by pressing
F8 before Windows started up. Windows 8PCs start up quickly so there's not enough time to press F8.
If the computer works properly please perform the following step.
Step 2: Place the computer in clean boot and check for the issue.
Place the computer in a clean boot state and then check if it helps. You can start Windows by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.
1) No error message. Laptop freezes a while and resumes as if nothing happened.
2) The latest Avira antivirus was installed.
3) The issue existed from the installation of win 8. Although i cannot confirm that it happened before the installation of chrome and avira antivirus. Another problem is that the card reader drivers are not installed, as the installation of these drivers
cause an error message: