Computer Problems

Earlier I was moving my computer around and set it on its back, which fucked up the on/off button on the back, on the power supply thing, i think thats what its called. And the button wont stay in place and sparks and smells like something burning and my computer wont stay on for more then a few minutes. So i guess i need a new power supply? But i dont know which one would work for my computer.. So i was wondering if you guys could tell me.
I plan on buying it off of

http://www.newegg.com/Store/Category.aspx?Category=32&name=Power-Supplies

What kind off specs do you need to know to know what one i should get?
Thanks.

 

uhhh. please be more descriptive. what type of computer do you have? like brand and model number.. or if its a custom, list the specs. we cant help you if you cant help us