How to inject LAN drivers into WDS Server BOOT images

We use WDS (Windows Deployment Services) to image large numbers of computers. Lately we have been using a Windows Server 2008 R2 WDS server with a Windows 7 boot image. However several times we have found that newer PCs/Laptops (manufactured after Windows 7) have trouble PXE booting in to the Windows 7 boot image, due to the lack of LAN drivers.
We found that these drivers need to be "injected" in to the boot image (a .WIM file) to enable the PC/Laptop to be imaged using WDS. After several attempts we found the following procedure worked quite well to achieve this.
Before You Start

• You’ll need a full install of WAIK (Windows Automated Installation Kit,) as it contains the necessary tools to manage WIM files. This can be done on any system, but if you’re running WDS it is best to perform the injection on the WDS server.