Avoid formating and repairing windows

Hi,

My little brother computer is freezing each time an application is open , surfing on internet is impossible it is getting blocked even when we are using Microsoft word.


I have been install avast antivirus and after full scan of the whole System no virus has been detected.


Want can be causing his computer to work slowly.


For my part my only solutions is to get the whole machine format but he don't want to take the risk of losing all his important files and also since he don't have the drivers for his computer.


Worst it he has integrated sound card and grafic card that we don't even know the trade mark.


Do someone has a better alternative ?