如何在installshield中删除默认的INSTALLDIR

I have a Basic MSi project in installshield 2012 that allows the user to change the installation path, the default installation path is a fixed path C:\xxx directory. The problem is that if the user decides to install the application in another location that the default C:\xxx folder the system will do that, but it will also create and empty C:\xxx folder! How can I prevent this?I have a Basic MSi project in installshield 201