Installed 5.0 on a Vista PC, but the Security Center shows a warning in the tray.
When I open Security Center it says that there is no anti-virus enabled (red box).
But it also reports that Avast! is installed as a spyware scanner (box below).
Version 4.8 reported as updated and installed both as anti-virus and spyware scanner.
Doesn't Vista recognize 5.0? XP does :-) Haven't tried on Windows 7 yet :-)