It is impossible to disable the Task Board.
GreenHopper is quickly moving towards all the features being in the Rapid Boards, and I would recommend you adapt your workflow to these rather than using the Classic Boards if possible.
If you still feel that you would like the option to hide the Rapid Boards, then I encourage you to file a ticket in the GreenHopper issue tracker here: https://jira.atlassian.com/browse/GHS
Atlassian Support - San Francisco
Enjoyed the support?! Tweet us! #atlassiansupport
Wow, I got swamped and now that I've finally gotten my head back above water, I find we have several new members! Welcome @Darren Keith lowman , @Amanda Babb , @Luis Zapata , @Joli Holmes , and @bh...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events