Answer
ArcPad’s default projection is WGS84. So, if you create a new shapefile in a blank ArcPad project your data will be in the Latitude/Longitude WGS84 projection.
To change your default projection you need to create an ArcPad.prj file and copy it onto the handheld device running ArcPad.  Follow the directions below:
- Copy or create a projection file that is in the coordinate system you want and rename it to ArcPad.prj.
- Connect the GPS or data collector to ActiveSync.
- Open the ActiveSync program on your desktop computer
- Double click on the ActiveSync Icon (Green Circle with two arrows) or
- Go to Start/Programs/Microsoft ActiveSync
- Click on the Explore tab in the ActiveSync interface
- Navigate to the My Documents folder on the Mobile Device and paste the new ArcPad.prj
- Now whenever you open ArcPad with a blank project, the coordinate system will be defaulted to whatever projection you created in the ArcPad.prj file