http://smartphonemag.com/forum/topic.asp?TOPIC_ID=18916

Q: Can I use my T-Mobile MDA (HTC Wallaby) as a desktop/notebook modem? A: The MDA (HTC Wallaby; a.k.a. O2 XDA, Qtek1010, Siemens SX-56 etc) can be used via a serial - either cable or IrDA - (but NOT ActiveSync USB!) connection. For this, you'll need a PPC2k2 (WM2003+ isn't supported!) ROM version that has wmodem. Please read this thread for more information.