i wouldn´t recommend to hook it up directly to the scroll lock power ´cause it´s rated about 3 volts and 20 ma for one single led. maybe connect through a optocoppler ( i hope it´s named so in english) or an electronical relai (need far less power than a mechanical one) because if ya hook it directly you would mybe burn you keyboard or the PS/2 connector of your motherboard (or even the entire board). that would be shit, but the idea rulez ;D. tomorrow i´ll start a prototype ;D (if you don´t mind to lend me ya idea)