When I install avast it automatically assigned an serial key? without even asking me ?
I downloaded it… however, the simple user interface is not working now … anyone know how to fix this?
A key can be obtained from Avast’s website as is clearly stated there.
About the ‘not working’:
Do you (or did you) have another av installed? If so which one?
What other security software do you have installed?
What OS?
Without knowing details it is not easy to give help. We are not mindreaders. 
The only key it could possibly assign is the Demo key (and you would still have to say to use this rather than enter your own key) and this would give you 60 days unrestricted use. After that you would need to register and have a key emailed to you (I’m assuming that you are using the Home, free version).
I apologize for not giving the details:
XP Home Edition
Avast Home Edition
It was a demo key…i have a key now. It is registered. However, we are getting closer to solving the issue w/ the Simple User Interface not loading… It might be WindowsBlinds or the Iconpackager.
Thank you for all the help.