Before you can deploy to the WM5 emulator with the VS2005 beta you need to download and install the 80Mb DMA transport update
Shut down active sync and VS before installing. Once this is in you can build and deploy to the WM5 emulator.
nb: the VS2005 package is really neat (honest). Converting eVC3 or 4 projects is easy so long as you install the project convert add on.