Have you tried Firefox or another browser. Internet Explorer is evil (although IE7 isn't too bad).
Absolutely DO NOT give this company a single penny. Worse comes to worse, you backup your important files and re-install Windows (I don't think you will have to re-install though).
Make sure you have UP TO DATE Anti-Virus on your computer (AVG FREE is good and obviously, free).
And, don't download "free" software unless it's common (Firefox for example), or from a large company. You probably got the problem from some sort of "free" software.