Most people aren't aware, but getting security software off your computer is surprisingly difficult and is probably the number one support question we get asked from store purchasers is "how do you fully remove an existing security suite?".
The problem is, often uninstalling a security suite doesn't fully remove it. Traces are left behind, particularly in the Registry. You then try and install new security and it refuses to complete the installation.
The solution is a dedicated removal tool and most security companies provide their own version of these removal tools. Malwarebytes is no exception, hence the Malwarebytes Clean Uninstall Tool.
Malwarebytes Cleanup Utility will remove all versions of Malwarebytes (Premium or Free) from your PC, plus older software such as Anti-Exploit, Anti-Ransomware and other tools.
Simply run the tool, reboot, then you should have a completely clean Malwarebytes-free PC which enables either to re-install Malwarebytes or another security suite.