This is not a duplicate of this question as it does not work: http://apple.stackexchange.com/questions/2389/is-there-any-way-to-set-a-macbook-pro-to-not-sleep-when-you-close-the-lid

I have a Macbook pro 2011. I want to be able to close the lid without the MBP going in sleep mode.  It seems InsomniaX is not doing anything.  I've seen people with MacBook Air having the same problem.

Does anyone have an alternative suggestion for that ?