Windows keeps telling me I have a virus and it wont let me open explorer?

Things keep coming up saying 'Virus Intrusion' 'Hijak' 'system danger' etc from windows and then a things from windows keeps coming up saying 'Get a copy of win 7 anti-spyware(RECOMMENDED) or continue surfing(DANGEROUS)' And it says you need to pay to download it so I've been trying to click continue to surf so I could go download another free anti virus and It wont let me, a box just keeps coming up telling me to download that. I think THAT is the actual virus, I don't believe that is genuinely windows telling me todo this? Anyways I found another way to get onto the web through my torrent client(it just appears to be the actual windows browser that wont let me use the web) and well I download 'AVIRA' and scanned my computer for about 2hours and it said it only detected one thing and put it into quarentine.. but the windows thing still keeps coming up. HELP!!!!!!