There's recently been a series of questions about using Windows XP Embedded for a robot chassis on the Seattle Robotics Society's mailing list that I've answered on my blog.

I also found some excellent work on calling into the Evolution ER1 Robot Control Module directly without having to go through the ER1's API. This is very exciting to me because I had some serious reliability and performance problems with the ER1 API that I can now studiously avoid. It turns out that the ER1 Robot Controller Module is actually a Pilot Motion Processor from Performance Motion Devices plus additional supporting hardware. In reviewing the Pilot's SDK, this is a very nice piece of hardware including A/D ports and Digital IO ports and a well documented RS-232 protocol that can run over a very high speed RS-232 interface (say, USB connected like the ER1 provides).