So my sister's computer is an older HP Pavilion and she has been using it for ages. It is a solid laptop but it is plagued with god knows what. I looked in the task manager and it was amazing what the thing was doing on idle. Anyways I need to just reinstall windows but I am not to sure how. I mean I know the whole process but where would i get my hand on a key or is there a way to figure out the key for this machine and then download and iso from somewhere on the net?