Uh, pressed accidently the "thanks" button... Most likely we cannot distribute that binary.Both the Home and Professional version of Windows XP come with the tool Tskill . In addition, XP Professional has the more powerful tool Taskkill.
Source: Managing Windows XP Programs from the Command Line: Taskkill and Tskill
I think it's best to use PsKill, and distribute it along with MediaPortal
It's a part of PsTools, which is a part of Windows Sysinternals, which is originally made by Mark Russinovich