How do i get mcafee off my computer ive tried everything but takening it in?

i have an aspire one d255 and the mcafee is screwing it up i want to get it off my computer but its acting like a viruse and i cant findd it any where on it. the only reson i kno its on my computer is it keeps asking me to buy it and its firewall is up. pl someone help me get this crap off my computer without spending to much money :(