Note that if you have a MS Smartphone (as opposed to a Pocket PC), it MUST be application unlocked for the hack to work. See for example See for example
Smartphone & Pocket PC Magazine Expert: Werner "Menneisyys" Ruotsalainen - WM6 & Microsoft Bluetooth A2DP (stereo Bluetooth headphones) quality: Light at the End of the Tunnel? for more links on application unlocking. Note that app unlocking is absolutely legal.