The Digital Reader 1000 supports Mobipocket format books natively, with no need to upgrade any of the software. You will however need to ensure that you have registered the Mobipocket PID for the device prior to downloading your purchases.
Here's where you can find your PID:
You can then log in to your eBooks.com account and download your Mobipocket format book to read on your DR1000.
The DR1000 can also be used to read unprotected PDF and EPUB files. These files can simply be transferred from your PC to your handheld device.
For further help with the DR1000 by iRex Technologies, please click here.