rootkit.gen - swerftx.sys infection

Question

I'm infected with rootkit.gen (specifically: swerftx.sys, unique code IQ1LCWD7) at LBA sector 0 of my MBR. It's a "highly severe" Trojan which can enable a remote computer to take over my computer, among other things. I don't want to pay Webroot $100 to remove it for me. How do I remove it myself, or where can I learn how to do so? Or is there too much to learn just to save myself $100, or does it require special software that isn't available to the average person? Should I use ComboFix? (I've got it, but I've heard it can be dangerous.) Help!