A little more information about this herd of trojans would be helpful ?
- What OS are you using? is it up to date?
- What avast! version and VPS file (virus database) number, e.g. 0436-4 (see about avast!)
- What was the virus name, what was the filename, where was it found
example (C:\windows\system32\infected-filename.xxx)?
- What actions have you taken to try and resolve the problem?
Are you saying avast doesn't detect them? - if so what did or make you think you have a herd of trojans?
Are you saying that avast can't delete or move them? - if so what error messages are you getting?