Q: Computer does not turn on

Hi. what mac OS are you running? Try a pram reset. Hold down Command/Option/P/R on startup for three chimes. If you are running an OS above 10.6 you could try starting to you restore partition by holding down Option R or the Option key at startup and use that disk utilities to check your startup disk. Or use single user mode.http://support.apple.com/en-us/HT203176

Hi. You could try a SMC reset.http://support.apple.com/en-us/HT201295 orhttp://support.apple.com/en-us/TS2570  also http://support.apple.com/en-us/HT201573 and lastly  http://support.apple.com/en-us/HT4718

Hold down the option key on reboot and see what startup disc options it gives you.

Pete