AVG not detecting a Virus - Need help quick!

Viruses & Threats
3

Angel, Have a look @ this article (http://avgclick.me/1DU8MTF).
AVG Guru

2

Angel, Have a look @ this article (http://avgclick.me/1DU8MTF).
AVG Guru

1

I know there is a Virus on my computer, because it's fine for a day, and then after it slows down until it is completely unusable. I opened my Action center today, and two messages popped up, telling me there is a Virus or unwanted apps before quickly disappearing. Whoever has written this Virus has somehow bypassed AVG, and makes my own computer think that everything is fine. I'm getting worried, as I don't know how this will be solved. Is there any way to detect this virus and elimate it completely?