BAKU Antivirus Scam minneapolis, Minnesota

I was on my computer when it notified me that I had a virus.  A screen came up that asked if I wanted to procede to a Microsoft site.  I said "yes".

Upon going there, this company wanted me to purchase anti-virus software.  When I closed out of the offer my computer would not allow me to log on. 

Only when I purchased this did the site allow me to go out of their offer and resume my work.

I have contacted my credit card company who tells me that they get this all the time.  They will remove the charge but are concerned that my computer may have a "trojan horse" that will require additional expenditure to remove.