Hey, we have been setting up WDS at my work for only Windows XP as Vista isn't suitable for our network yet.
Just thought I'd put a few things in that I have learnt:
You can run wds in mixed mode or native mode - Mixed mode lets you use RIPREP images while migrating to wds. I dont know much about RIS as we have previously been using ghost with a sysprep image - moving on since the ghost license is expensive.
A boot Image is a winpe image -
You need the boot.wim from the Vista DVD to be able to access a menu of all suitable install images as it contains Setup.exe.
Install Images are images that have been sysprepped and captured using wdscapture.exe or imagex.exe from a winpe image.
wdscapture is like a gui for imagex that will let you capture and also upload a sysprepped image.
If an image doesn't show up in WDS on the client pc it is because the HAL doesn't match the computer - the setup program has a detection which was bad for us as we use a script to update the sysprep.inf so it changes the hal to the correct version - we overcame this by using an autounattend.xml file to force choosing the image and then running scripts after setup.
Longhorn - Deployment Technet Forum can be a good resource if you run into any problems.
WDS can be a bit confusing at first.
You will want to install WAIK for customising winpe wim files.