You've been wasting a lot of time. Microsoft has their own product for managing their own images. It's called Microsoft Deployment Toolkit (MDT). You can use it to deploy/update XP, Vista, 2003 Server, and Server 08. It stores the files in a .wim format. It's pretty neat, as it uses a write once type database so you can have multiple images in 1 wim to save on space.
At work we use a single image to manage over 200 different computer models that can be deployed in a myriad of ways such as LiteTouch methodology which you can use either Microsoft s Deployment Server to push via PXE boot or just the good old fashion thumb drive. Or you can use the ZeroTouch methodology and use SMS to update/deploy systems without any interaction (Good for kiosk type systems).
In a nutshell, MDT takes all the best practices for deployment (Litetouch, ZeroTouch, Automatic driver injection, user state migration, etc.) and rolls it into one application.