It's not that hard!!
If you're using XP here is the folders you need to check/delete AFTER you save your good .ahx file.
C:\Program Files\ActiveHome Pro
C:\Program Files\Common Files\X10
C:\Documents and Settings\All Users\Application Data\X10 Settings
C:\Documents and Settings\All Users\Application Data\Active Home Professional
for the registry stuff go Start,Run, regedit and it will open up the registry editor. BE VERY CAREFUL USING THIS!!
Open the Edit tab and select Find (Ctrl +F) and type in ActiveHome and it will find all the instances of it in your registry. Delete the stuff it brings up and hit F3 to find the next instance until it's done. READ WHAT IT IS SHOWING YOU. If it's not obviously AHP stuff leave it there. You can do a 2nd search for X10 as well.
Reboot and reinstall and you should be good to go. If you're worried about the registry stuff then just do the folders and reboot and it may work.