Malwarebytes won`t install, run or update – How to fix it
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If Malwarebytes Anti-malware or any of your security programs won’t install, run or update, then you’ve probably got malware or the effects of malware on the computer (some types of malware will disable Malwarebytes Anti-malware and other security tools).

Malwarebytes Anti-malware or any of your security programs won`t install
Fix 1: Before saving Malwarebytes Anti-malware or any of your security programs, rename them first.
You clicked on a download link and a Save dialog opens. Change file name and click on Save. For example, before you save Malwarebytes Anti-malware, rename mbam-setup.exe to something like mapp.exe (or use any random name) and then click on Save and save it to your desktop. Double Click mapp.exe to install the application.
Note: several good names that you can use: explorer.exe, iexplore.exe, firefox.exe, userinit.exe

Fix 2: Change Malwarebytes Anti-malware or another security program installation file extension.
Turn on “show file extensions for known file types” by doing:

Double-click on the My Computer icon.
Select the Tools menu and click Folder Options.
After the new window appears select the View tab.
Put a checkmark in the checkbox labeled Display the contents of system folders.
Remove the checkmark from the checkbox labeled Hide file extensions for known file types.
Press the Apply button and then the OK button.
Now your computer is configured to show file extensions for known file types.
Right-click on an installation file (mbam-setup.exe for Malwarebytes Anti-malware) and replace .exe extension with .bat, .com, .pif, or .scr. Press Enter and then double-click on it to run.

Malwarebytes Anti-malware or any of your security programs won`t run
Fix 1: Rename the main executable file.

Click Run, type %ProgramFiles% and press Enter.
Open a home folder of your security program, right-click on the main executable file and click Rename.
Type a new name (try explorer.exe, iexplore.exe, userinit.exe or any random name like 1j2j3kkk.exe) and press Enter.
Double-click on this file to run.
An example for Malwarebytes Anti-malware. Click Start, type in Search field %ProgramFiles% (if you using Windows 2000/XP, Click Start, Run, then type in Open field). Press Enter. Open Malwarebytes’ Anti-Malware folder. Right-click on the mbam.exe file, select Rename, type myapp.exe and press Enter and then double-click on it to run.

Fix 2: Boot your computer in the Safe mode.

Restart your computer.
After hearing your computer beep once during startup, but before the Windows icon appears, press F8.
Instead of Windows loading as normal, a menu should appear.
Select the first option, to run Windows in Safe Mode.
Run Malwarebytes Anti-malware or your security program.

http://forums.malwarebytes.org/index.php?showtopic=86493