Page directory Help

My installer uses the standard directory page to allow the user to select an installation directory. For this particular application the root directory of the drive is a valid location. For example, C:\ or D:\. My problem is that the directory page does not allow me to select the root directory of a drive. The next button is grayed out unless I select subdirectory.

Is there a simple solution to this problem?

Thanks in advance.

AllowRootDirInstall true

Stu