The latest upgrade of AVG Free found the bastard! "Trojan Horse IRC/Back Door.SdBot.145.0". Actually, both my machines had it on it, as well as a number of Alexa probes. But the thing didn't appear to have my slower machine as badly tied up, so I was able to get the AVG Free (7.0x) download and its latest virus definition downloaded; it was that latest virus definition that found it. (Running AVG Free 7.0 w/o the latest definitions didn't find it...)
Anyway, both PCs are surrounded by ZoneAlarm, and have latest AVG Free, SpyBot and AdAware running. Damn! Grygus is right...if this is what it takes to keep your machine "safe" running (if that's the correct term) Windozw connected to the net, then his timeline for making the entire net useless is right on schedule!
And in answer to Another Scott who posited whether the SP$ disk was OK...it did pass inspection. However, consider this: On my "slow" (read: older PII 400MHz) machine, I wiped the disk, then loaded SP4, then ZoneAlarm, then updated it to its latest version while running its "older" self, then installed SpyBot, updated it to its latest version, then ran it...and it found Alexa. Is Micros~1 shipping Alexa with its software? Andrew?