Property定义：Properties are global variables that Windows Installer uses during an installation.
比如，对于安装部署项目，在注册表里默认的HKCU\Software\[Manufacturer]
这里的 [Manufacturer]就是一个属性。
再如要将安装的路径写入注册表时的属性TARGETDIR。
添加一项：Name:foo Key:[TARGETDIR]
To use properties in your installation, you can get and set property values from programs using MsiGetProperty and MsiSetProperty and include as part of conditional statements in the installation database.
要设置一些Property，需要通过Installer的API如MsiSetProperty。
参考：
Getting and Setting Properties
Windows Installer Best Practices