I'm using Japanese IME on Windows 7, and I like to use Ctrl + Caps Lock to toggle between English and Japanese. In the past, when it would toggle to English, it would be half-width alphanumeric. Suddenly it's changed itself to switch over to full-width alphanumeric, even if it were just toggled to Japanese from half-width. How can you change this back? I didn't see anything in the properties window for the Japanese "keyboard" in Region and Language.
First of all I think you mean Shift + Caps lock and not Ctrl + Caps lock.
Second: You do what you want like this:
Control panel > Region and Language > Keyboard and Languages > Change Keyboards > Japanese > Microsoft IME > Properties > 'Editing' Tab > Editing operation and behavior > Key Template > Check
Ok your way out of all the open windows and the next time you toggle with Shift + Caps lock, your English will be Half-width