When You say uninstall ShadowUser and then install & REGISTER Avast. Do you mean uninstall Avast AFTER uninstalling ShadowUser?
You can uninstall both, in any order.
Then install avast first, register, then install ShadowUser. I'm just guessing that something is blocking avast from save the info to windows registry and it could be ShadowUser.
I ask this because Avast is currently installed. It works fine and in harmony with ShadowUser for some time, then I get this advert inviting me to buy Avast and a note telling me my license has expired (Which it has not)
If I then put in the license details in Shadowmode it works OK. (until the next time)
That's the point... avast license should be added 'outside' of Shadowmode... maybe...
If I do not do the latter step, but instead, come out of ShadowMode (Back to normal WinXP operation) Avast home is working properly licence key is installed etc. no problem
If so, the problem only occurs 'into' ShadowUser... The support of the application should address a way to solve this... avast 'registry modification' should be save or you'll have to add the key each time...