YAC (Yet Another Cleaner) is an anti-adware that installs a browser toolbar without your permission/knowledge. YAC will also replace the homepage and search engine of your web browser. If you have a page with the search.yac.mx URL that pops up during your browsing session, it means that YAC is already present on your PC.
Remove from the YAC from the Control Panel
Open the Control Panel > Add/Remove programs.
Select YAC (or any suspicious application) > Uninstall.
If you can't file the program, go to Computer > C> Elex-Tech
Search for the uninstaller and run it.
AdwCleaner is freeware that can remove most PUPs, adware, browser hijackers and malicious toolbars.