I was recently working with a client and he had military time running on his Windows clock in Windows Vista. If you polish your shoes and have perfected the making of your bed, here is how to set military time in Windows Vista.
Click the and type region in the Instant Search field (Figure A).
From the Regional and Language Options window, click the Customize this format button, and select the Time tab (Figure B).
Choose HH:mm:ss and your military time (Figure C) will now be displayed. See you tomorrow at 1300.