Wow.... I just attempted another install of ZoneAlarm (I haven't used it since I moved to Vista 64 back in February '07) and the installer had to be opened in compatibility mode just to run itself. It's frustrating how developers can't do a simple f***ing version check and allow 6.1.7600 as well as 6.0.6001, 5.1... etc. I had a good laugh as soon as the ZA installer told me I had to upgrade to Vista SP1 before I could install it under Windows 7. As I said already, running the installer's executable in compatibility mode for Vista SP1 fixed this, but it's still so sad, it's laughable.
Edit: Now this is even more laughable. The ZoneAlarm install was blocked due to compatibility issues. For the record, this was a freshly downloaded copy of ZoneAlarm Free 8 from the Zonelabs website.