Clean Install - Advice Please

My powerbook is running slow! There's drag & such in windows (scrolling etc) and stuff is taking ages to load. Hence, I want to do a clean reboot of my system and start again from scratch.

Concerns. I'm a little worried about getting all my stuff working again (I use Logic Pro, Reaktor, MS Office and a bunch of the Apple programs that come on the machine) - I've not been so good at logging passwords/codes etc... Also, I'm a little afeared re: getting my internet installed again. It's all been registered etc, and I'm a little concerned that it might not go back on the same!

So; any suggestions where I can find my passwords etc, and, more importantly, how I can keep my wireless network (airport!) intact (It's got WPA protection; can I find my WEP key anywhere on the system?) I've got a harddisk ready to go for backing up all my documents etc...

HELP! Ta. Tom

Yeah, thanks guys...

Boot from the CD/DVD that came with it and run disc utility from the 3rd screen in. Let it repair permissions and just check the disc for problems. Then boot back to the machine, go download an App called "Cocktail" and run all of the UNIX cron scripts that it will let you. That should help a lot.