[stomachmonkey]

Sometimes when they have been off for a while they take a long time to boot.

If the internal PRAM battery is dead then it could have lost a lot of settings. It may not be able to find the startup disc.

Hold the Option key when starting, makes it display all boot volumes. If it can't find, does not display one then you may need to reinstall the system.

There is a safe mode same as windows.

Hold the Shift key while booting it up and it bypasses everything but the essentials.

It also clears out crap that may be keeping it from starting.

If you have another Mac laptop and Firewire cable with you then you can try the hold T key at startup for target disc mode and mount on the other laptop then run Disk Utility and see if it can repair the mounted volume.