When I reinstalled it and then did the reboot I noticed that the first splash screen that comes up when its rebooting says
Welcome to Avast Home Edition and has all kinds of info about upgrading to professional if you need/want better protection.
When you reinstalled...
But before or after you've add the registry key?
4) Registration number is the same no matter what version it says.
It's impossible! I mean, are you inserting the right registry key?
The registration data is stored in value "RegData" of the key HKEY_LOCAL_MACHINE\SOFTWARE\ALWIL Software\Avast\4.0
However it's in an encrypted form. You have to had access permission in registry "HKEY_LOCAL_MACHINE\SOFTWARE\Alwil Software\Avast\4.0" key.
5) WHS console avast tab shows the version on this vista pc as pro.
Again, I'm only used to PC version, not WHS.