If you are trying this on your PC I am not sure as the locations seem to have changed when we upgraded to windows 7.
On a windows mobile device the files for your customized tool bars go in two places.
1. Your preference files (APX), and custom scripts (vbs) go in My Documents-My ArcPad
2. If you have custom Icons then those go in Program Files-ArcPad-System
Hope this helps.
Bryson