Before we start, If none of this works, you can use LiquidSquid's Guide, which will most likely have what you need there. Anyways, lets go!
Malwarebytes is known for being decent at removing R.A.T.s. It is paid, but before you start throwing tomatoes at me, the free trial is free (obviously). You don't have to put your Mom's credit card number with those silly little numbers on the back. (Also, if any Anti-Virus asks you to put in details, don’t do it! The R.A.T. isn’t removed yet, and if they haven’t already, they will steal that info.)
Autoruns is also good at removing R.A.T.s. Yes, this is stolen directly from Liquid's guide, shush! Anyway, here’s what to delete:
.scr filesQuick note: Make sure you are SURE that what you are deleting isn't important. You want to keep your PC! (I’d hope...)
Make sure you didn’t turn off anything in Windows Defender, like Real-Time Virus Detection—you need that!
Too scared that it’s lingering on your PC? Do a factory reset, and make sure you do it correctly!
R.A.T.s sometimes hide fully in your files, so if nothing is detected and you're sure you have one—or just want to be safe—factory reset!
When the R.A.T. is gone, RESET YOUR PASSWORDS! All of them! For example, I had the same password for almost FIVE years. Don’t be like me! (It's changed now, don’t get any ideas.)
Some R.A.T.s hide in your BIOS, so they can stay even after a reset. It’s not that common (at least from what I’ve seen), but don’t take my word for it. If that’s the case, well... good luck.
Literally this whole site was by Lock (NotMageLock on Github), all I did was write the guide, I don't even know how to code. :P