I would first run the Latest McAfee Getsusp Tool, to detect any Suspicious/Unknown Programs on your system. Plus this Tool will automatically send detections to the McAfee GTI Data Base. Simply remember to enter your Email address under "Preferences" before scanning.
Then I recommend running this Excellent Removal Guide:Remove MyStart Search Protection (Virus Removal Guide)
To keep Malwarebytes (Free) DO NOT accept any Free Trial Offers/or activate the Pro/Paid Version throughout the entire Download/Installation process.
You may find these two articles most informative,and give you a general idea of how this "Nasty" arrived on your system:
All the very best,
McAfee Volunteer Moderator
I also noticed you mentioned (YAC). This is yet another piece of Potentially Unwanted Program, that is "Bundled with other programs also. The Removal Guide I inserted above should resolve your issues. However, if by chance (Yac) still persists to cause issues.
You may refer to the following Guide:How to easily clean an infected computer (Malware Removal Guide)
I reiterate (only) if the need to arises. Go with the Removal Guide I suggested in Post #1. Just thought I would add this,to cover all bases, if you will.
Kindly post back your results, especially if you need further assistance.
All the best,
Removing Mystartsearch is't so difficult. You can make it without inatlling any additional software using .dll library file.
You should for the start download file from http://removalbits.com/how-to-remove-mystartsearch-com-homepage-and-search-from-opera-firefox-chrome...
and add it follows the instructions to the right directory. That's pretty easy I think. Try some and good luck.