Insecure internet activity

Hello,

I was using my laptop last night and all was fine. This morning, however, I turned on my laptop and clicked on the internet explorer. Instead of taking me to my homepage, a message appeared.It read:

Insecure Internet Activity. Threat of virus attack.

It says a few other things then has two options. One says to click here to get full time protection and continue browsing and the other continue to this website unprotected (not recommended). When I click to get the protection, it takes me to perfect defender 2009.

Along with that Windows Security Alert pops up sometimes telling that the firewall as detected a virus, but all the options are enable protection, it takes me to the perfect defender 2009 as well. I don't know what has happened, since just last night it was working fine. Any suggestions?