Virus and spyware infection

While surfing around tonight I started getting warnings and popups(disguised as warnings). My antivirus(Avast!) did pick up a couple of trojans and moved them in the vault. I still suspected more . Getting a pop bubble on the taskbar saying "Warning: Your computer is infected". Well I said to my self "Duh". If clicked on erroneous popups ensue warning me of an infection and I should download a certain software. Suure I will. Anyway I scanned first with Avast! Antivirus which turned up zilch(other than what it had already found previously).I ran my Spyware Terminator which only found one file which wasn't the problem. So decided to try an online scan from BitDefender and so far has found 2 viruses infecting 3 files so far and still scanning. Also I still get an annoying popup saying"Security Monitor:Warning! Attention! System detected a potential hazard(trojanSPM/LMX) on your computer....bla, bla etc. Of course when clicked on the same popups urging me to download a certain software(same as before). We'll see how it goes.