Computer kept shutting down and now won't start up?

Ok so I went to burn a DVD the other day with MKV the and my computer shutdown. So I started it back up and thought nothing of it and started to go on the internet and it shutdown again, it did this 3 times until it wouldn't even turn on anymore. I hit the power up button and it would start to power up and then shut off in about 3 seconds. Anyway, I took the fan out and cleaned it, tried to start it up, no go. So then I took the rest of it apart to see if anything was wrong about 10 times and it still wouldn't start. I finally saw these 4 long chips back to back in the thing, and they each had a white lever on each end of each chip as if to hold it in, I pressed 2 down, The one's on both ends of 1 chip, but didn't remove the chip, I pressed the power up button and the computer started up. Once i was on I pushed the chip holder things back down and it was still ok, so i don't know if that's what made it start or if my computer just decided to start up at that time as a fluke. Anyway, I don't know when this thing is going to shut down again, so I wanted to ask if anybody knew what the heck is wrong with my computer and why it keeps shutting down? thanks