|This is a CPU: http://cdn.cpu-world.com/CPUs/Penti...|
This is a CPU box: http://www.hothardware.com/articlei...
Please refer to your computer as a "computer" or a "tower". CPUs do NOT have any buttons you can press.
To expand a little on kuwese's suggestion - the PSU (power supply) is basically a transformer. It takes AC & converts it to DC, then breaks it up into several different voltage rails, +3.3v, +5v & +12v. If any one of the 3 rails is defective, you may still get signs of life (LEDs, fans, etc) but the system itself will not boot. The answer to the question about hearing the initial beep at startup is important.