Console application, Loading internally

Hey, I'm working on my own sort of command prompt, including all my functions i use on computers, etc. My problem is when i call a function for example taskkill, it opens it in a new window, and doesn't let me see any of the output, is there a way for me to call an external program internally to see its output?

Also, I forgot, I'm using VS C# 2010 Framework 4 on Windows Vista.

Relevant link: http://www.dotnetperls.com/process-start

Also, why reinvent the wheel? There are lots of good command line replacements for Windows, notably Cygwin and PowerShell.