I can recommend something far better then Malwarebytes as well as most other programs looked over in the past several years actually. In fact I bailed someone out when his older XP machine was hit with a bogus av program that created a new admin account and locked him out of running almost everything on his desktop!
The VIPRE Rescue Program is what I have to give thumbs up on for finding and removing just about bug on a Windows system. VIPRE Rescue - VIPRE Computer Recovery Solution from Sunbelt Software
First you download the main executable seen there which will then create a new folder to unpack files into. Immediately it goes to work scanning the entire OS drive in what looks like your typical command prompt window. This one red marked scores of bugs on the infected machine tested on and that was after removing the System Protect I-Worm infection.
Note the name was taken from an actual freeware that places a guard on the system regiatry and made to look like a regular av program in the email ads! Unfortunately my friend simply clicked on the spam and wound up with a big problem
the free program there was able to clean up real fast!
I gave this a go on the old case here just replaced and that found a trojan inside a zip file still being stored for XP on one of the storage drives! This should find any keyloggers or rootkits, trojan downloaders, or other bugs rather fast when used! This is now being stored on a flash drive made up for data recovery stiick and would be the idea free tool to try out on the system in question.