I lose internet connection every 20 mins to an hour

Is this the only PC that disconnects - do other devices connected work OK - if so how are they connected to the router - wireless or wired

Please post back here the make and exact model of the router and if you have a separate modem, the make and exact model of the modem.

Please make a note of the status of the lights on the modem and on the router when working normally - post that light status here.
Now when the internet disconnects make a note of the status of the lights for the modem and router here again. also note which have changed.