DavidR
2
What is the infected file name, where was it found e.g. (C:\windows\system32\infected-file-name.xxx) ? Check the avast! Log Viewer (right click the avast ‘a’ icon), Warning section, this contains information on all avast detections.
Why can’t you remove it, what did you try ?
What errors are displayed, etc. (or does it keep coming back) ?
What Operating System are you using ?