Hi there !
I just heard that Avast should work on Vista RC1 but obviously i installed the wrong version of Avast Home (11.550KB setupger.exe) now i downloaded the probably right beta (41.100KB setupful.exe) but i CAN’T uninstall the previous version of Avast, which has the Program-Incompatible-Issue 
When going to Software - Remove programs - Avast - Deinstall i get an RunDLL Error message which says “Loading error … Modul not found” (its in german and i translated here myself)
Please help me how to uninstall that not working Installation of Avast ! I dont wanna reinstall whole vista just to get rid of that wrong Avast installation.
Or do i just have to over-install the other beta Version of Avast ?
EDIT: ah sorry, just found that aswclear.exe on this site and it appears to work 
sincerely yours hannibal