I have ransomware

First, I was wrong, I have Vista.
When my computer started to malfunction, little windows on the bottom rt. kept popping up saying, "file... is at risk, run your antivirus software".
After much of that, a large window came up "MS Tools Center (at least MS something)" Then below in the window were options to purchase virus protection, diff time lengths & prices.
So I picked the cheapest ($60) and put in my cc info. Luckily my card was maxed out, so the transaction was declined.
I copied down the unlock code yesterday, don't see it today. Does it work, and where do I put it?
I have my computer password protected, so do I put it into the password bar?
Please help.
All my business files are on there and all of my research. I'm dead in the water right now.
Thank you!