Most of your questions are answered in the manual, please try and read it from start to finish at least once.

Your problem is that the characters "%", "@" and "$" have special meaning to KiXtart. To enter them in strings you need to double them up, so you need to write the following string:
Code:
"@@%%SystemRoot%%\system32\SHELL32.dll,-22921"


This is explained towards the start of the manual.

Also look at using the option SetOption("NoVarsInStrings","ON") as this may help you.