Hi Malcolmd and welcome to the WTT forums.
Sorry to hear that your notebook computer wont start.
A little more information would be helpful....
1 Make and model number of your computer
2 Operating system installed and service pack level
3 Do you have a complete backup copy /archive of everything that is importnat to you on your computer keft safe on removable media?
4 Do you have the Microsoft Operating System Installation disc, or a Manufacturers Restore disc?
5 You say your computerwent "off on you" can you provide an amplification of this extra information description etc
6 Have you disconnecected the Interne cablet ,emptied any disc drives, removed CD/DVDs flash drives, memory sticks and any printers scanners or other USB devices (have nothing at all connected to it and then removed the battery, connected the mains electric wire (via the supplied power supply unit) and then held the "power on button down for 15 seconds.....then waited 30 seconds and then pushed the power on button once..... if not please try this and let us know what happens.
7 Are any fans running on the laptop when you try and power it on? (look underneath ,listen and feel for vibrations indicating a fan turning....
8 Are any lights visible anywhere...look carefully all over the machine....
Please give a full report ...remember we may be many thousand of miles away from you so we must rely upon your observation skills and ability to fully describe exactly how your computer is reacting if we are to assit you.