Many of these spyware/adware programs keep the anti-virus programs in the dark by intercepting any reads of the registry. They are able to do this by actually replacing part of the windows kernal. When this happens you cannot get rid of the virus using any program if you have booted off the hard drive. The only way to get rid of the virus is either:
1. wipe the disk, and reinstall windows
2. make a bootable windows CD, boot off it, and use Spybot S&D to clean up after that.
If you don't have anything important on the PC I would bite the bullet, and choose #1. I've done #2 for Windows XP, and was able to clean everything off but it was a lot of work.
Making a bootable windows CD is not real easy. Microsoft doesn't support it, but some resourceful people have figured out how to do it. I've never done it for windows ME, but I found a web page that describes how to do it:
bootable windows ME CD
Good luck, Hugh