Normally, if you install Ghostscript before you install Scribus it will be located automatically (because the Scribus installer will locate it and insert the correct path to the executable in the settings).
So, if you try to wipe the Scribus install and re-install it you might get Ghostscript working.
I just wanted to open a new thread, as I discovered this discussion about exactely my Ghostscript problem
Just after I installed Scribus 1.4.rc5,
I installed Ghostscript
Windows lists the installation as
GPL Ghostscript Artifex Software Inc. 2011-10-17 9.04
In the meantime, I installed
Scribus 1.4. version where rotate problem solve
But I have still the message at starting Scribus "Ghostscript is missing"