This is a tiny chip just to the south of the cpu socket. No idea what it does but it seems happy giving off infra red radiation none the less, whatever it is it does. Leave it alone, its only doing its job!

According to Holst on the AOA forums...

"The ATXP1 chip you listed as "little chip" controls the overtemperature protection on XP processors by reading the Xp internal diode then cutting power to the board if the temperature gets too high."

What I want to know is, what protects the little chip?! ;-)