Thanks. Unfortunately, I can't seem to download anything because I no longer have permission. I'll try to set up a bootable drive from my Mac and plug it in once it's ready.
Wish I knew how I ended up in this mess...
You can format the USB to FAT32 on the MAC, download Kyhi's PE ISO onto the MAC, mount the ISO to see the files in it, and copy the files over to the USB stick. Then boot the Windows system to the USB stick and run Malwarebytes.
Thanks a bunch, everyone! I'll try to get the PE rescue media first. If that doesn't work I'll have to boot back up from the USB.
Or burn the ISO file to CD using the built-in Disk Utility on your Mac.
As far as I know, just copy the contents of the ISO file to USB and it might doesn't work.
It appears I have fixed the problem.
I accessed command prompt and typed "shutdown /r /o". From there, I went into safe mode, and was able to restore administrative access to my main account. Everything seems to more or less work.