Monitoring the referrals to this site, I'm getting an increasing number of hits per hour from Google, people looking for sachost.exe or sachost.exe removal. I've also had some e-mails thanking me for the help. Anyway, if you're a visitor looking for help on disposing of this trojan, the instructions are here.
I suppose I should put in a disclaimer about "use these instructions at your own risk", but won't. Use common sense. If you're not sure you can follow the instructions ( editting the register is open-heart surgery on your computer, it's really easy to kill the patient by one small slip ), then go find a tame geek. They'll be glad to help, if only to show off their prowess.
I've also received a second e-mail that attempted to infect me with a Trojan - but now my defences are a little better ( there was a Microsoft patch from April 13 I didn't know about), and I don't even know which trojan it was, it didn't penetrate far enough for me to ID it. Be very careful of any e-mail whose header is Question for seller -- Item #nnnnnnnnn where nnnnnnnnn is a 9-digit number.
More details on people's experience with sachost.exe are available on an e-bay forum.
If this has been any help to you at all, please consider hitting the Tip Jar, as it's been 4 months since my last pay cheque. All major credit cards and Pay Pal accepted. But it's purely voluntary.