We ran into the same problem -- people want to keep their wall charger in their briefcase. We didn't want to push out the cradles, since we thought we would have to load the software to make them charge, and we don't want the software, since we are syncing everything wirelessly with the BES. We found that we can make the units charge in their cradle without the Desktop Manager software in Win2000 and WinXP this way:
Plug in the cradle to a USB port and cradle the BB. Windows should say new hardware found, RIM handheld (or something close to that), and it needs drivers to use the device properly. Point the install to drive that you have rimusbnt.inf and rimusb.sys, and it should load the hardware. It should now charge without the Desktop Manager. Hope that helps!