sorry to say, sometimes it’s the best, safest way forward.
you know those backups you’ve been taking of photos, etc? Be prepared to use them.
if you haven’t backed up, get the drive into a USB cradle (25-50$ at Jaycar), grab what you want to save (or take an image of the hard drive if you can) & extract files as possible.
Then take the time to tidy cables, make sure you have the install keys you need, the drivers you need for at least internet access and spend a few hours getting everything up & running.
PM me if you want some remote assist.
i do this sort of stuff often. Part of the job, but usually get the junior on the PC’s.
While it’s possible to spend time malware scanning, etc, (based on what you describing its malware) there’s a point where you get to not finding any more malware on a machine but that doesn’t mean it’s clean. It may mean that it’s really well hidden, or you haven’t looked everywhere.