How to fix Dual graphic card problem? Nvidia and Intel

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http://askubuntu.com – I recently installed Ubuntu alongside with windows 8, but the problem is that the fan is constantly running and I believe the problem is that my nvidia card is always running. My laptop has two graphic cards. Intel Graphics 3000 and Nvidia GT540m. I would like to only use Intel card, and nvidia only during games and such. if anything I’m okay with disabling nvidia card, because i can play games on windows 8. Thanks. (HowTos)