This isn't a PSPad problem, but your problem and knowlegdge of MS command line.
If path contains spaces, you need to enclose it into double quotes: "D:\Eigene Dateien\Programme\PSPad\csstidy.exe" "%File%" -- <http://forum.pspad.com/read.php?2,54975,54986> PSPad freeware editor http://www.pspad.com
