|What happens when you try to boot without pressing any keys.?|
The facts the the laptop is turning off at the very beginning would indicate a hardware problem. This could be anything from a faulty power supply, overheating or failing hard dsik. You can only find out by a process of elimination.
Try booting the laptop from a bootable CD and see if that works. You may need to go into the BIOS to set the CD as the first boot device.
F10 should get you into the BIOS configuration screen and that doesn't need a hard disk or an Operating System to work. You need to start tapping F10 as soon as anything appears on the screen. You can also try F2 or F6 which does the same job on some laptops. There should be an indication on the initial screen to say which key to press to enter set up. If you cannot get into the BIOS se tup then it could be a faulty keyboard or something more serious.
Pressing F8 once the OS has started to boot will give you a boot menu with an option to boot into safe mode.