I've never attempted to disable it -- but I've changed it.
Essentially what you are doing is editing the About file.
Go to Skins, and select the skin you are using. In the
Toolbar area, click About.
You can change the image that appears on the button itself (I
use this to put in an image containing the project name and a
logo), and what appears when you click the button.
From your other post in this forum, it looks like you're
working with FlashHelp rather than WebHelp, which is what Rick's
link in this thread is about. I responded to your other post with a
link to Rick's Web page on fixing this for FlashHelp--the file for
X5 worked for 6.0 for me. (Thanks, Rick, by the way!) Good luck,