How to repair hijacked “Hosts” file

I have a stand alone client that has been hijacked my malware that redirects or prevents from entering a search site and it has altered the Hosts file and is preventing programs such as Spybot, Malwarbytes, et al from working as they apparently need access to this file(s) to work. I see many fixes for this, some contradictory and counterintuitive but no clear consensus. Does anyone have experience in this area or can point me in the right direction? There are many claims out there that ultimately do not work.