I wouldn't do any major upgrades without a PCI card to do the work of your onboard hard drive bus. The on board HD bus in a Yikes! G4-350 is (gulp) 33Mhz. It is a carry over from the G3 Yosemite B&W board. Let it rest in peace. I would bypass 100Mhz Ultra ATA entirely, and go for a Serial ATA 150Mhz controller card and hard drive. The pricing is quite comparable already, and the benefits in terms of performance, improved cabling technology, and future upgrade compatibility, are hard to argue. I know of several Serial ATA controller cards available- these are the standouts- There is a basic one available at Macgurus that will support two internal drives, and it is dirt cheap- this is it: http://www.macgurus.com/productpages/sata/FT1002.php If you gotta go hog wild, and want a card with the potential to support four drives of limitless size, get the Sonnet Technologies card- this is it: http://www.sonnettech.com/product/tempo_serial_ata.html but you'll find it cheaper here: http://www.amazon.com/exec/obidos/tg/detail/-/B0000DZFJI/qid=1075631827//ref=sr_8_xs_ap_i6_xgl23/104-5505744-8388706?v=glance&s=electronics&n=507846 Check for Serial ATA drives on rebate sales weekly at CompUSA. They run 50-60 cents a gig on sale, about the same price as the regular old Parallel ATA100 drives. Seagates and Western Digitals are, as of this point, the fastest and quietest Serial drives available. The Maxtors are converted ATA100's that aren't a true 150Mhz, last I heard. You might not find one on sale this week, but check back next week- subscribe to their circular, and keep an eye out for unadvertised specials. You'll be surprised at the deals these guys will come up with. KEEP COPIES OF YOUR REBATE DOCUMENTATION!! I've had to follow up like a pit bull to get my money from them in the past. Incidentally- without the onboard controller card, don't buy anything bigger than 128Gigs. Good luck. None are so hopelessly enslaved as those who falsely believe that they are free. - Goethe.