I think I got hacked yesterday and I need some help. Here's how it went down

tldr I need 1) advice and 2) a new w7 iso from a reliable source. Please provide details of where you got your iso from and how you know it's trusted. This probably isn't the best place to ask but I'm looking everywhere I can)

>night before
>reinstalled a few games and updated nvidia drivers
>yesterday
>browsan yt, working in docs in other monitor
>kb+m stops working, capslock still noticably working
>comes back to me in 2 minutes
>suddenly, all the windows close out
>then the taskbar disappeared. Nothing but a wallpaper
>spooky-ass pop up message
>"stop what you're doing i'm in control"
>"hello."
>at that very moment i was spooked as fucking hell and immediately powered off my PC and disconnected my ethernet
>rebooted and ran malwarebytes. Killed 88 trojans
>i'm still suspicious as hell about whether I was actually hacked or not in the unironic sense
>reconnected with ethernet for the past 12 hours. Nothing suspicious so far but this is suspected hacking we're talking about

I need a new w7 iso i think. I don't have the slightest clue how this "guy" got to me. So far my friends say it's probably the w7 iso i got (source is on the installgentoo wiki's w7 page), and I'm probably going to run DBAN and reinstall. Where can I find w7 iso's? A google search is NOT helping at all, just like how it was when I initially installed, which is why I request for any advice and sources for w7 here. Thanks for reading this post