Occasionally, I see a question about determining if a given installation is MOSS or simply WSS. I am unaware of any Object Model method or property that indicates this, but I did find a different way. The User Profile service is a web service that is included in MOSS and not WSS. So, if the asmx file exists, then MOSS is installed.
Here is a code snippet:
string isapiFolder = SPUtility.GetGenericSetupPath("ISAPI");
string userProfileServicePath = Path.Combine(isapiFolder, "UserProfileService.asmx");
bool SharePointServerInstalled = File.Exists(userProfileServicePath);