After an attack left me unable to play with my pooter, I did a reformat of the C drive, reloaded all the software - MS XP Pro, Printer, Scanner, remote keyboard, MS Office Professional, Adobe Photoshop, Firefox etc. Then I reloaded Norton A/V, Blackice, Spybot, AdAware and HijackThis, did scans on the clean machine and saved the logs.
Any difference between the clean machine and anything added without me knowing about it now becomes more obvious.
Tedious I know, but what the hell, at least my machine's clean now. I dunno what was 'phoning home' before but I've had no infections or take-overs since doing that. It only took a day and I had to be there for just an hour or so of that. I'd certainly do it again any time my PC starts behaving in an odd way.
BTW, as well as being burned onto CDs on a reglar back-up schedule, I keep my data files - Word Documents, PDF files, and photos etc. - stored on the "D" drive partition, which remains untouched by the above process.