Here i present you the CAT File Packer / Unpacker 1.5
I've just completed it.
It is a standard Win32 GUI application.
It can handle of both 1.2 DOS CAT files and Windows CAT files with perfect compatibility.
I've attached it and its sources to this post.
EDIT: I've just updated to version 1.5. Now it can handle adlib.cat, roland.cat, etc.