i had this same issue... i had to rerun the WEI a few times after initial RC install, it kept wanting to install something, on a few boots, not the same thing, it was installing new things like usbroot hub stuff and mass storage etc, but i never could explain why THAT beyond changing any kind of hardware, would it want or need to rerun the WEI. I came back from running it the first time, and i think thats when (afterwards) windows installed found peripheal hardware,( besides sound nic camera and graphics -all were already installed). I noticed aero gone (which to add after initial install and desktop logon, i didnt have aero by default, wasnt the case in 7000) again, so i ran the WEI again.
Knock on wood, i havent had it do anything like that again. But there does seem to be somekind of overall issue with it.
this dealt with a mobility x1600 by the way with 7 assigned drivers