Look at these links.
What Macs natively support large IDE drives? (over 128GB formatted)
http://forums.xlr8yourmac.com/action.lasso?-database=faq.fp3& layout=FaqList&-response=answer.faq.lasso&-recordID=34188&-search
How Big a Hard Drive Can I Put in My iMac, eMac, or Power Mac?
http://lowendmac.com/macdan/05/1024.html
Using 128 GB or Larger ATA Hard Drives
http://support.apple.com/kb/HT2544
The Power Mac Storage FAQ
http://forums.macnn.com/65/power-mac-and-mac-pro/246391/the-power-mac-storage-fa q/
Possible Alternative - SpeedTools ATA Hi-Cap Support Driver: Allows the use of extended capacity ATA drives (drives greater than 128 Gigabytes in size) on older (Pre Mirrored Door) G4 and G3 Macintoshes running MacOS X versions 10.2 and later. Cost $24.95
http://www.speedtools2.com/ATA6.html
Possible Alternative 2 - Larger than 128GB drives can be used by adding a PCI ATA/100 or ATA/133 controller card, one which is 48-bit LBA compliant; or by adding a PCI SATA controller card and using SATA drives.
Cheers, Tom 😉