Microsoft never misses opportunity to upset customers : DRM protected eBooks in MS Reader format not working in Windows Mobile 5.0
October 07, 2005; [Pocket PC phone]
Microsoft is working on the solution but in meantime if your eBooks are in Microsoft Reader format and protected by Microsoft's DRM and you switched to Windows Mobile 5.0 Pocket PC phone edition device, then you can't use them anymore! Apparently this problem applies only to Pocket PC phone edition devices! Not to regular non-phone PDAs with Windows Mobile 5.0!
So if this issue is important for you, you may wait with buying till this issue will be resolved....
* more...
Found this here;
http://msmobiles.com/
I have an X5, so I don't know. I thought some people would like to see it though.