I am having problems with CreateShortcut

Make sure you have separated the parameters from the target file.

For example, if you want to create a shortcut to notepad with $INSTDIR\Readme.txt as a parameter, don't use this:

CreateShortcut "myshortcut.lnk" "notepad.exe $INSTDIR\Readme.txt"

Instead, use two separate strings:

CreateShortCut "myshortcut.lnk" "notepad.exe" "$INSTDIR\Readme.txt"