It was tested with Tornado Smartphone Platform with recent firmware update. It could work with other phones and even with PDAs, hovewer I cant be sure about compatibility, as I had to break some specifications to defuse "anomalies" (bugs?) in the propietary HTC/OMAP USB hardware driver.

When activated, memory card will not be accessible in the smartphone, as all direct access to the flash card will be routed to USB. Take note that if some currently running programs have files open from the storage card, that can prevent Mass Storage from activation ("error 1f"). In that case, try to close all running programs (soft reset is needed sometimes).

Application installed to "Accessories" Start Menu subfolder.

Windows Mobile 5 is required. Sorry, but I cant possibly make it work on WM 2003, as only WM5 allows USB protocol implementation separate from USB hardware driver - on WM 2003 Ill have to rewrite whole USB hardware drivers, and of course its not feasible.

If you want to uninstall it, I strongly recommend to de-activate mass storage mode first.

Of course, you will also need full application unlock. Take note that some recipies do not do full unlock, they still leave some API locked. People who getting "error 57" most likely havent fully unlocked their smartphones. Try this one:
to HKLM\Security\Policies\Policies
add new value "0000101b": dword = 1

That would set security model to "one-tier" - unsigned applications/components will still ask for confirmation, but after you confirm, they will launch in full-trust access mode, like on WM5 PocketPCs.

Update Description:
v1.32:
- Added possiblie explanations to most common activation errors (1f and 57).

v1.3:
- Added prompt to soft-restart the device after installation.
- When storage is attached to USB host, mobile device USB controller and flash disk are ordered to be kept in "Power On" state.
- Added switch to choose between "Removable" and usual ("Hard Disk") device classes. Will affect how the host OS treats the device - for instance, it will not create System Restore and Recycle Bin if class is Removable.

v1.21:
- Added some additional diag checks to help evaluate possible problems.

v1.2:
- Added write-protection switch.
- Added checks for ability to actually open memory card (card existance).
- If "storage card" installation chosen, will install to main memory anyway, as it cant properly run from storage card.