Yenc powerpost and others don't have an installer, so you can't find it in your control pannel under ad/ remove software, instead you must manualy delete the directory in your Program Files directory.
Since Powerpost doesn't write info to the Windows register, it's very safe to do that.
Maybe you've got some shorcut's on your desktop or in your start menu, delete those as well.
Why deleting it anyway?
It doesn't give you much space, the program is less then 1 megabyte...
Good luck!