How do i know what kind of power supply goes in to my computer?

My current power supply is pretty noisy and i want changes, so can anyone tell me do i need to find a specific power supply to match my motherboard or can i get any power supply to go with my board? my computer is a ibm netvista and the model number is 6579, its pretty crappy. Also if i get a power supply that is big in watts can i upgrade the cpu, hard drive, memory, graphics, etc? Thanks for your response?How do i know what kind of power supply goes in to my computer?
there will be a sticker, usually on the back of the computer, that tells you the power usage Volts, Amps Hertz and maybe watts same for the monitorHow do i know what kind of power supply goes in to my computer?
Turn your computer off and unplug it. Open the case. Carefully remove the cables that connect the power supply to the motherboard. Write down what cables go where or if you have a digital camera, take close-up shots. Then carefully remove the power supply. Take it to the computer store with you and tell them you want one like it. You can ask about upgrades there also.