Best way to fix these is with a utility disk like
Kaspersky Rescue Disk which is a CD you boot from, so whatever's on your hard drive doesn't get a chance to run. You scan from the utility on the CD, and since the malware doesn't run, it can't interfere with the scan. This thing gets the rootkit part of those fake AVs, too, which Malwarebytes misses a lot of times (the reason they come back just when you think you've fixed them.)
The fake AV things are pretty much just fraud, they don't really destroy anything but they can make your computer unusable, trying to force you to pay for the "protection." The Windows Recovery, though, is nasty. Catch it in time you're probably OK, but once damaged it's really quite difficult to get everything back like it was.
If you see any of these things present a window, do not respond to the window in any way. Don't try to close it, don't try to minimize it, don't click on anything. none of the Windows features presented are necessarily the actual Windows features. The red X may actually be programmed to be the Yes button, giving the malware permission to install. So if one of these pops up, just yank the power cord before it can do anything else.
Seriously. That's the best prevention once the screen presents itself.