Sojourner, do you use any download manager (like FlashGet, Dowload Accelerator Plus, GetRight, etc.)?
If so, you will be an option into its settings to add the following line:
"C:\Program files\Alwil Software\Avast4\ashQuick.exe"
This will set the download manager program to use ashQuick (the quick scanning module of avast) to scan the downloaded file when the download finishes.
Generally, you must use that line without any other parameter. For example, with FlashGet.
Some applications, to proper use ashQuick, need a parameter so you will write:
"C:\Program files\Alwil Software\Avast4\ashQuick.exe" %d
or
"C:\Program files\Alwil Software\Avast4\ashQuick.exe" %f
Do I make myself more clear?