This is especially good for the Treo 700wx where the battery meter is tough to replace (hasn't been done yet).
I like it b/c I get a % for my battery read out! Much more informative!
Basically, download this app. No installation needed, just put the .exe in a new directory on your device along with the .reg file and click the .reg file to add it to your Registry.

Then launch the app.

Holding down your stylus on the clock/battery will bring up the Settings screen.
What makes this app great (besides it's tiny size and free) is that it is completely customizable:
- all colors can be set
- you can move the battery/clock anywhere on the start bar
- you can increase/decrease the background size
So what I did was move it over the existing clock/battery and made it just fit over them to cover the old ones up.
(*
Note: I do not know how to change it from military time! Sorry!)
Have fun and play with it!