Need external hard drive for Mac osx 10.4.11

Hi,
I am getting ready to upgrade our Mac OSX 10.4.11 from Tiger to Snow Leopard 10.6. There are lots of pics, music and pdf files on it. Concerned that I will lose them when I add memory and Snow Leopard. I am looking for an external hard drive to store before I start the process.
Anyone know where I can find one?
Anyone still operating a 10.4.11 system?
Thank you,

External hard drives can be purchased from just about any store that carries computer equipment. You can either shop on line or in person. The only thing to keep in mind is that most external hard drives are pre-formatted for Windows and will have to be re-formatted to use with your Mac. You should also consider making a backup of your old hard drive. Older versions of Carbon Copy Cloner or SuperDuper can be used for that purpose.

You can DL SuperDuper from SuperDuper! (Mac) - Download. Great and easy App to clone your HD.
As chscag posted there are a lot of Ext HD formatted for Windows out of the box, and for this reason i use Western Digital MyBook where thay are plug and play for a Mac. Meaning you dont need to reformat it to take your Mac Backups