Ah, you only need one anti-virus. I made this mistake last year. I thought that by having two anti-virus' that my computer would be doubly protected. Then it stopped working altogether. I later found out that it was equivalent to wearing two condoms! And these anti-virus things were fighting each other to protect my computer!

It's possibly that you accidently downloaded the other antivirus, stick with the one you know. Go to add/remove programmes and you should be able to stop the extra anti-virus programme.