Step 1: Go to your control panel (Start > Run > Control)
Step 2: Once you reach the Control Panel go to "Regional and Language Options"
Step 3: On Regional and Language Options click on "Customize"
Step 4: Now go to "TIME" Tab
Step 5: Here you can change the variables "AM" and "PM"
Step 6: Change these variables to your First name or anything for instance.
Step 7: Click Apply -> Ok ... for instant effects on your taskbar.
As soon as you click OK, you should immediately see the changes in your taskbar clock located at Bottom Right corner of your system. Incase there is no change keep reading.
Step 8: Double click on the digital clock in taskbar to open "Date and time dialogue box" ...Look for the digital time format eg. 03:50:50 AM
Step 9: Click on the "AM" or "PM" to edit. You could change them using your arrow keys.
Step 10: Once you see your name, click Apply.