UPDATE (later the same day): there’s another, brand new utility to clean up the PIM data on WM5+ devices,
PocketOutlook Eraser. As of current, 1.1 version, it requires Compact Framework 2 (CF2) to run. CF2 is integrated into WM6 devices – but not into WM5 ones. You’ll find the CF2 installer CAB file
HERE. Also note that, as opposed to the initial version, it already creates a link to the main executable.

(WM6 Smartphone screenshot)

(WM6 VGA PPC screenshot)
(Thanks to my blog reader
John for the
heads-up!)