This is a modified version of the Stardock CursorXP-to-XCursor conversion script by Eric Windisch (MIT Copyright). The drop shadow feature didn't work for me in the original, so I changed the code.
How to use:
Unzip your Stardock CursorXP set into a directory, change to the that directory, and run this script (perl sd2xc.pl, or just make it executable). You'll need Perl-Magick installed, as well as the Perl Config module and perhaps others.
If you want drop shadows, run it this way: "sd2xc.pl --shadow". RTFSC (read the fine source code) for more options and details, although not all of it works.
With just the above defaults, the "cursors" directory you create will be in a subdirectory called "theme". Rename it to whatever you want and move it to /usr/share/icons, after which you can specify that new cursor set in your default/index.theme file.
The original Perl script: