First off, there is no such thing as a clean install of Mac OS X. Please read this FAQ:
http://discussions.info.apple.com/webx?14@72.pBFlaGIfVaV.0@.599b7ba4
And learn why the terminology "clean install" is misleading and should not be used when referring to Mac OS X.
Since you have an 8 week old Powerbook, you should already have a CD burner. Use it, if not an external hard drive to backup to:
http://www.macmaps.com/backup.html
It is not a question of if you will lose data, but when. And during a system upgrade is one of the more likely times that would happen, but it can happen at anytime without warning. So two backups you can rely on are a must for any computer user, unless you want to play russian roulette with your data.
Secondly, since you have an 8 week old Powerbook, you can upgrade the RAM, add any of an assortment of cameras, VHS to DVD converters, audio devices, etc... Firewire and USB offer many different devices you can connect to. And if your Powerbook is a 15" or 17" then you have PCMCIA/Cardbus as well. For more on compatible hardware and software, see this FAQ:
http://www.macmaps.com/macosxnative.html
Keep your hard drive less than 85% full, and enjoy it.
And because you got a Powerbook, save up enough money within the first year to buy AppleCare. You'll be glad you did. It may not cover accidents, but it will cover any minor manufacturer defects that might crop up through the hardware test. And best of all, you may even get your Powerbook replaced with a newer one under AppleCare if you find you do have a defect after a newer model is released.
You have that whole first year to purchase AppleCare within. And you get valuable 7 day a week tech support for up to 3 years from your computer's purchase date if you purchase AppleCare.