EDIT: People who knew what they were doing beat me to it. Try theirs first. I'll leave this for completeness' sake.
I'd recommend booting a linux distro with GPartEd from USB, wiping the Classmate, then retrying the imaging process.
Just my $0.02 as a self-employed computer worker.
NOTE - I can't test this, and don't know if there's a hidden recovery partition you shouldn't touch or anything. Just check before wiping, and maybe dd to an external (CloneZilla does a good job).
Recovery distro I use for this kind of thing:
http://partedmagic.com/doku.php
You can use UNetbootin (
http://unetbootin.sourceforge.net/) to install it to a USB drive and boot that, though I've generally had more success with external disk drives. Try the USB image first; it's faster.
If you use the USB stick, please, PLEASE,
DON'T use the Classmate image.