What is APIC????

I have it enabled on my ABit nf7-s.

What is it?
Should it be on or off?
If it should be off, how am i supposed to go about shutting it off?

Advanced Programmable Interrupt Controller

APIC provides multiprocessor support, more IRQs and faster interrupt handling and is supported by win nt 2000 and xp.
if your os supports it leave it on for the faster irq handling.

if u want to change it i think it would require a reinstallation of your os.

if your system is running ok leave it alone