Inactive Hijacked desktop

[Inactive] Hijacked desktop

I have a win7 pc and it has been hijacked, there is a second partieon that is running a netwrok as well as hijacked my whole pc, everything that i have tried has failed, the next day everything is back to normal, i rest the harddrive to the orignal factory settings by the next day everything is the same, i have an idea this could be someone in the home so i need to know how do i get my pc back and then lock it so nobody can do this again. My broweser as well is hijacked.