I'm almost certain that you've got the handicapped features activated on his user account. This would mean that instead of holding down shift to multi-select, you have to tap Shift to toggle it on and then tap it again to toggle it off.

Start, Settings, Control panel, Accessibility options. Make sure to turn off all features, and go into the settings of each feature to deactivate the "hold down shift to activate" and such.

If all those features are already turned off, report back.