LogicPD provides a Compact Flash driver, and I've used that successfully. If you've already bought the MMC/SD card, though, that may be of little solace.

The fact that LogicPD has provided so many of its own drivers leads me to believe that a Microsoft provided WinCE driver may not be the solution. Their software may work on, say, a PocketPC, but I don't think that's a guarantee that it will work on an LH7A400. Hardware drivers normally are, by definition, hardware specific.

I'm new to this embedded programming thing myself, so I could be wrong. After all, I thought the benefit of having a common OS was that one program would work on multiple machines. Part of me says it shouldn't matter what sort of chip you're running as long as the port type and card type is the same.

I don't happen to have an MMC card on hand, so I can't play around with one to find out.

Hope that helps,
Pete