Looks like a FET (Field Effect Transistor); likely part of one of the VRMs. I'd guess it's the SB's VRM.
It definitely won't work without it. I'd suggest trying to get warranty, but you're probably out of it. If you're handy with a soldering iron and can find an exact match on the part (I can't read the number from the photo; it's difficult to get the light just right), you could maybe replace it.
Also, I'm fairly sure that's not a P5KPL - this is:
SATA ports aren't in the corner on this one, amongst other discrepancies.
Running a board with a fried component is highly dangerous to your other components.
Best course of action is to buy a new motherboard. You could try replacing the part, but you never know what else was damaged.
Depending on what it was powering, before it fried, it may be possible that the board will work, but some functionality will be lost (like SATA ports not working etc).
Thanks for the reply,
Sorry for the confusing post.
The motherboard is p5kpl-cm. http://in.asus.com/Motherboards/Intel_Socket_775/P5KPLC...
I was able to start the pc normally.
Didn't lose any functionality like sata or anything.
Just, wanted to be sure if it will affect my other components in long run.
What might be the cause of this?
Psu or loose wiring?
Was using corsair cx500.