Computer keeps restarting

I have a lenovo ideapad p400 and recently when I turn it on it only lasts about 6 min. Before it restarts again and after that it does the same thing. It started when the brightness button wouldn't work so I tried to fix it but accidentally uninstalled the display adapters and since then it won't work how can I fix it?

Since you deleted an important file, you need a driver update.
Control Panel\All Control Panel Items\Windows Update