Helop with the extortion web page scam, please.

Hello,
 
I use the webroot internet security version of webroot.
 
My question is:
 
How do I know if the "pay us money to unlock your computer" webpage (virus/trojan) has been fully deleted?
 
My situation is:
 
I contracted this virus/trojan today. Webroot apparently didn't catch it. although my computer was locked up. (taskmanager would not work) I was able to "log off" and restart my computer. I then ran webroot; it detected nothing. then I ran spybot; it dectected something and I deleted it. then I downloaded malawarebyte and it dectected something and I deleted it.
 
I have rebooted twice since then and everything seems fine. I also reran webroot scan and nothing appeared.
 
So, does that mean that my computer is safe or is this something that lurks around and causes mayhem later?
 
I am concerned as I use this computer for financial transactions, periodically.
 
Thank you in advance for your help and as you can probably tell I am not a sophisticated computer person.
 
Thanks!