[psiphi]

Microsoft only required PPCs to be flashable in the last CE version (2003?), so there is a good chance the devices don't support flashing, especially if they are knockoffs...

Even if they are flashable, unless you have access to drivers for the devices, and they have enough Flash memory to support the OS, you won't be getting too far without breaking some functionality... If you have an exact model number, it would be easier to work out what is possible...