Ok, the package is extremely large. and yes it is exceeding 20 minutes to complete the installation which is mostly a file drop. However, this message box is enough for the average user to abort the installation;
I used LZMA compression on this installation. I am going to try again with CABs instead. But I need to get the 7GB of files down to 4.2 so uncompressed isn't going to work, and I really don't want to make a multi-disk release of this.
Another problem I have with compression is the extract path defaulting to [AppDataFolder]. [AppDataFolder] is accessible to the Current User only. The correct path should be [CommonAppDataFolder] which would be the same for all users and allow for Repair/Upgrade/Patch sequences for any administrator not just the one that did the original installation.