First few months in IT? Welcome to hell...

I'm kidding (mostly), I'm in IT also and if you're in for even a few years, you'll start to build a collection of horror stories like this one. We've all seen things you wouldn't believe.

So you need to have full buy-in from the owners. If you're able to talk directly to them, then it sounds like this isn't a huge company. If you clearly explain in a professional way to the owners the situation with documentation and they don't fully support you, leave the company asap.

As somebody who has been involved in multiple ransomware recoveries, trust me...you don't ever want to deal with a rogue unsecured machine on the network. And owners that don't care or take that risk seriously are absolute fools and this will only be the tip of the iceberg of stupidity.

That computer is a ticking time bomb. Please for the love of God tell me that your boss doesn't have local admin rights on his system.

If the only thing your boss uses that system for is to connect to a web app to manage inventory, why is he mad about switching from windows 7? Does he just like how windows 7 looks visually?

I guess it doesn't really matter. Also, windows 10 isn't a long term solution because it also goes EoL next year in October, so you'll be in this same position in less than 2 years.

You can either go to Windows 11, or if you wanna be a little wild, install a Linux distro like Mint on there and theme it like Windows 7. You solve the security problem and he gets to pretend he's still in the early 2010's.

Honestly though, start looking for another job if the owners don't support you 100%. IT is already a stressful and intense enough job, you don't need stubborn idiots like your boss to add flavor.