Well if you do a clean install, it wipes it completely. The hard disk is erased, so anything you want to keep, you need to back it up.
Drivers, look up the hardware and download the latest ones.
Programs, make a list and make sure you have all of the installers to hand.
All the documents need backing up for all users and shared documents, (made the mistake of forgetting shared docs and lost 6 months of pictures).
Remember to do Windows Update as well until there are no updates left. Then run CCleaner and Eusing Registry Cleaner, and defrag it, and you should be left with a nice fresh OS, all up to date, and cleaned out so it should run nice and quick.