Installing Windows can be a chore. If you need to do it often--for instance, if you're a company that builds its own white boxes for internal use--then you need a pre-installation tool to help you.
Bart PE is one good choice. It's free, easy to use, and is supported by a growing user community. In short, it's the administrators' best friend. Check out this review I wrote awhile back for WindowsDevCenter. But please be aware of the Windows EULA and how it applies to this product.