My Mac is taking too long to turn on (more than 15 min and is still thinking)

Try the steps described here:

http://support.apple.com/kb/ht3964

1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
   Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.

Try doing a NVRAM/PRAM reset - after you have done this - go to system preferences - startup disk and select your hard drive as the startup drive and restart your Macbook again.

Resetting NVRAM / PRAM

1. Shut down your Mac.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6. Release the keys.

After resetting NVRAM or PRAM, you may need to reconfigure your settings for speaker volume, screen resolution, startup disk selection, and time zone information.

Ok - Do you still have your original install DVD?

If so, turn your macbook on while pressing down on the options key - boot on the DVD and run disk utility and verify your disk - Do not repair any errors unless you have your files backed up. If errors are found - restart your Macbook and back up your files then run disk utility again and repair your disk if errors are found.

If you are unable to find a solution here, make an appointment at an Apple store genius bar.

https://discussions.apple.com/docs/DOC-3353

Ciao.

Click on the link below to see which Apple Store you're close to in France.

http://www.apple.com/fr/retail/storelist/