You need the Windows CD, keycode, a windows boot disk for formatting the hard drive (which I recommend) and all the applications you want installed. Wiping it clean means reformatting the hard drive. You'll need a Windows boot disk if it is Windows 98. Windows 2000 & XP do everything from the CD so you don't need a floppy boot disk. The process is easy to do but lengthy to write. Do you have any one who is a reasonable techy that could help you through it?
If you can't find the keycode sticker or COA then download Belarc Advisor from belarc.com, install it, run it and print it out. You'll have a printed copy of all of your systems components, software and key codes. It's a good record to keep for emergencies and really helps to find the right drivers if you don't have athe original install disks or driver disks for the laptop.