it depends on which G4 you have.
If you have a quicksilver, not without some heavy and scary to do mods. There isn't a stock power supply that delivers the requirements of the QS mobo.
If you have an AGP, then yes.
<a href="http://rett.org/powersupplyinstall/" target="_blank">http://rett.org/powersupplyinstall/</a>
If you have a yikes, then probably, since it's similar to B&W G3.
<a href="http://www.xlr8yourmac.com/systems/MacinPC_ATX_case/Blue_G3_to_ATX.html" target="_blank">http://www.xlr8yourmac.com/systems/MacinPC_ATX_case/Blue_G3_to_ATX.html</a>
<small>[ 07-18-2002, 03:09 PM: Message edited by: robot prom ]</small>