PC-Cleaner

last Saturday I started getting this pop up on my desk top to scan my computer possible Trojan or virus. from security center. when I click next it whats to install PC-Cleaner ???? on my task bar a icon shows up which lends me to their site.I BELIEVE ONE OF MY FAMILY MEMBERS activated THIS BUT NOBODY KNOWS!
Please can you tell me how to remove this everything I have tried prefelch,regedit all virus scans with three different programs all show clean NOTHING has not worked.
Thanks for any comments