A hard drive is a hard drive -- there's no such thing as a "Mac-specific" or "Windows-specific" hard drive.
The PowerMac G4 computers used an IDE (commonly referred to as ATA, PATA, IDE or EIDE) bus for their hard drives. You would need to purchase one of those kind for it to be compatible. These are different from the more recent and more common "SATA" hard drives. "SATA" = "Serial ATA", which is not what you want -- you want "Parallel ATA."
Also be aware that PowerMac G4 computers somewhere prior to the Mirrored Drive Door models cannot natively support a hard drive larger than 128GB. If you want to put a hard drive larger than that in there, you have two options:
1) Purchase a PCI expansion card that supports hard drives larger than 128GB (or supports 48-bit LBA).
2) Install drivers, available for some amount of money ($20? I don't remember...) that "patch" the operating system into tricking the hardware into supporting more than 128GB or something... I don't recommend this route, but some people use it flawlessly, so, to each, their own.
You can install a hard drive larger than 128GB in that computer, technically, without doing either of the above, but you'll be limited to using only 128GB of the disk in total -- even if you try and get crafty and say, "Hey, I'll just make TWO partitions on the drive, each less than 128GB!" Nope, sorry, ain't gonna happen... the computer will "see" any drive larger than 128GB as a single 128GB drive.
If you have OS 9 installed, then you can simply drag-and-drop everything from one drive to the other and retain bootability. If you have OS X installed, then you will need to perform a "clone" operation to retain bootability using software like Carbon Copy Cloner or SuperDuper.
