Computer completely freezes(screen, mouse, keyboard) some minutes after starting

Hello!
I have a mini laptop running Windows 7 Starter. It started having problems some months ago and hasn't been used since then. It starts normally and after some minutes it freezes completely, which means that the screen freezes, I can't move the cursor using either touchpad or mouse and the keyboard doesn't work at all. I have tried a few combinations like Win+Crtl+Shift+B, Win+R etc. and nothing changes. What can I do?
Thank you!