Rufus is usually the tool of choice. You’ll need MCT from Microsoft to download the ISO.
If the PC was infected by malware, it would be best to nuke the system drive, at least.
Make sure no Host Protected Area has been set up, otherwise the malware could either damage the computer again, or (worse) operate silently.
Depending on the specifics, you might even want to go as far as to toss the system drive and get a new one.