system
3
The unpleasantness may have installed itself as a Process in which case the file is locked and cannot be deleted.
Start task manager and click on processes. If you can find the name of the offending file in the process kill the process and then delete the file with a dos box, windows explorer or use try avast again.
Might be worth looking in the registry startup section to see if an entry has been made to start the thing automatically. If so delete this entry if Avast hasn’t done it for you.
Cheers
Chris