I wanna get a new HD for my g4, but I have a question, Are the hard drives the same for Mac & PC or do I have to find a hard drive that is only for mac if so where can i find a good deal on one that is at least 160gb - 250gb?
Just to expand a little on Drew's answer, the hard drive file format system is different. Mac uses HFS+, PC uses NTFS.
Mac will read, but cannot write to NTFS. That's why it's no good for backing up files from a Mac.
PC can neither read from nor write to a HFS+ disk. A NTFS disk is okay for transferring files to Mac, but not vice-versa.
If it's simple file swapping from PC to Mac you want to do, have you considered a flash drive? Up to 8 Gb now, and cheaper than a hard drive. It will transfer files from Mac to PC and vice-versa as long as it's formatted FAT32.
Update: There is a product called "MacDisk" for Windows that will permit HFS+ formatted drives to be read in Windows, by the way.