In preparation to install Tiger and finally wave goodbye to OS 9 on my five year old Power Mac G4, I swapped out the factory 40GB hard drives for a new pair of 120GB lovelies. These are the largest drives you can install using the stock ATA controller. I wasn't in the mood to pop for a new card, so these puppies will have to fit the bill. Regardless, it's four times the storage space... and the price was certainly right.
Prior to starting the project, I burned four DVDs worth of sanity check backups. There's also two copies of everything from the original drives on the 2TB file server in the basement. The drives themselves are still intact and bootable. You can never be too careful.