>I'm trying to use the Visual Studio Installer (v1.1) and I can't seem to be able to specify a target directory other than the four preset directories. In others words I can't specify "install this app in c:\myapp"
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That's correct - VSI uses one of four possible CSLIDs for the target directory, and provides no method that I've seen, even ORCA, to override this. You can use a third party installer that supports Windows Installer technology like InstallShield Express 3.0, InstallShield Pro for the Windows Installer, or Wise to create a custom action that would permit this - VSI 1.1 does not permit you to create custom actions.