Are you using WDS by itself or are you using MDT to go with it as well?
With WDS by itself you only need a bootable flash drive, network connection, and a share on another machine to cap the image.
Boot from the flash that contains, windows 7 or some form of win 7 rescue. You need to get to the command console. Then capture your image... imagex /compress fast /capture <drive>: <drive>:\image.wim "Dell Latitude ST TABLET"
once it captures then : net use x: \\server\share /user:domain\username
now just copy <drive>:\install.wim x:\install.wim
If you use MDT then it is something totally different but you can still use this method then import your captured wim into MDT