Just thought it might be useful for others to know…
I found it impossible to deploy the netclient version via adnm onto clients that already have the pro version installed.
The result is no program group for avast and no tray icon, but the add/remove progs lists avast as installed. The knock on is you cannot then receive vps updates on those clients or push program updates. Also, the console cannot then find those installs.
The best approach is to first remove avast pro through add/remove progs then reboot then delete remnant avast/alwil software folder from program files.
This may be peculiar to the SBS version as I installed on SBS2003R2 Premium SP2.