Well, Kaspersky seems to have been better at rooting out the root kit than anything else I tried. First it found the vector that had been used to install it (a bit of freeware I downloaded a month or so ago that didn't seem to work -- it installed a generic malware installer that then installed the rootkit) and then a few hours later found what I suspect was the rootkit itself (an invisible trojan hooked into my winlogin process).
I don't know if that was everything, or not. I'm stopping for the night though. By morning my bittorrent of the latest Knoppix DVD will be done and I'll try another scan while running in Linux. If everything checks out I'll boot up normally, let things run, and then check my router's logs to see if I'm still spewing spam. I'm strongly hoping that I won't be at that point.