There's a beta version of Windows Mobile aka Pocket PC 2003 being distributed online. I have used it on my Siemens SX56 prior to the A.20.17 ROM/A.20.10 RS flash and I must admit the beta is a bit on the buggy site. A few times I had to warm boot it after the welcome screen froze up, some software that worked with PPC 2002 wouldn't work with WM or would stall out, the signal strength seemed weaker than the OEM ROM and battery time appeared less. From what a PR person at HTC, the company behind the XDA, O2, SX56, etc., has stated, HTC's working with Microsoft to iron out the wrinkles with WM before it gets released to the various wireless carriers. If you decide to try the Windows Mobile 2003 beta, BACK UP YOUR ROM & RS FIRST so worst case scenario, you restore the ROM back to OEM via the Wallaby Boot Loader.