Can you lose an email completely without blowing up the hard drive? I thought that the boffins could get just about anything up on the monitor

You can electronically "shred" them, but you still leave enough clues behind, such as time stamps.

Just more of the same -- what we have come to expect from the Bush Administration --INCOMPETENCE

All they have to do is what they've done with a lot of evidence. Ship it overseas for recycling, incinerate and powder the discs, and 'Upgrade', to a new model, with new hard drives and say they're just trying to keep up with the latest advances in technology. They sure seem to have the 'money' for something like that.
Does GWB know how to write Emails? or open them? Why learn, he's too busy running some country or other.
He's obviously not smart enough to cover his tracks.