Removing Malware

I downloaded Malware bytes Anti-Maleware. I was able to install it but I can't run it. Once I click on the program, I get a message saying "Application cannot be executed. The file mbam.exe is infected. Do you want to activiate your antivirus software now?" Does anybody know how I can fix this?

Thanks!

Please download the current version of HijackThis from HERE

• Double click and run the installer.
  
• It will install to C:\Program Files\Trend Micro\HijackThis\hijackthis.exe
  
• After installing, you should get the user agreement, press accept and Hijack This will run.
  
• Select Do a system scan and save a log file. This will open a notepad file of everything Hijack This found, copy and paste it back here.