Well I sometimes prefer my windows clock to relay in Military time than the standard look. I decided to do some searching and found a rather good article at annoyances.org and decided to relay it for you all.
Set the Windows XP Clock to or from Military Time
1. Click "My Computer"
2. Open the Control Panel
3. Select Time Options
3a. Classic View: Open Regional and Language Options.
3b. Category View: Date, Time, Language and Regional Options.
4. Click "Change the format of numbers, dates, and times".
5. Select the "Regional Options" tab.
6. Next to the box that shows your selected language click "Customize".
7. Click the "Time" tab.
8. In the "Time Format" box enter:
8a. Standard Format: "h:mm:ss:tt"
8b. Military Format: "HH:mm:ss"