Antivirus 8 ransomware issue

Antivirus 8 software downloaded and install itself on our home computer which is actually rogue spyware or ransomware. The Avast software did not give any warning or try to stop the Antivirus 8 from installing. Now the computer is giving us the blue screen of death because after it scan our computer and we did not purchase software it did not want to uninstall itself never the less I thought had removed the software but I guess it fooled me :'(. Now the computer will not access the internet or run the avast software. I found this website this morning and many other that tell the same story. http://www.removal-tool.org/Remove-Antivirus-8.html I purchased the avast! Internet Security 5.0 to prevent this from happening. The avast software is no longer running I tried to get it to work and only get a warning message telling that the software is not working.
What can I do now?

Important that you follow the guide step by step, so read it all before you start

Remove Antivirus8 or Antivirus 8 (Uninstall Guide)
http://www.bleepingcomputer.com/virus-removal/remove-antivirus8