Where did you purchase it ?
What version of AIS did you get, the latest version is 7.0.1426 ?
You should have received the license file and that is license.avastlic (not license.dat, etc.), double clicking on the file should insert the license for you. Trying to manually copy it may be what the problem is.
How did you install it, e.g. did you first uninstall avast5 free ?