To remove XCALC you just need to delete a few files. You know where you put the executable xcalc and the help files (html subdir). Delete them. In addition, you will probably have the file xcalc.ini in the same directory (or more precisely, the directory made current when you start xcalc). Delete that one, too. Nothing else!
But please send me an email if you thrash xcalc, and tell me why.