Malwarebytes anti-malware is a malware detection and removal tool. It's a really good one that I used frequently. How it just "showed up" is a mystery. I would go to your Add/Remove Programs page and see if it's listed. If so, do a Remove on it. Then you may want to go to the link Lisa provided and do a download of it. That way you'll know you have a clean copy to use. It's free, and it's good.