The purpose to unlock the Windows Phone is to sideload any application *.xap files into your windows phone without the need of marketplace. I’m lucky because i got the activation code from Microsoft to activate my windows phone OS on HD2. If you do not have the activation code, unlock and sideload apps maybe is the best and only way to install windows phone app in your windows phone 7.5 Mango HD2 device.
How To Unlock Windows Phone 7.5 Mango On HD2?
1. Download WP7 Update Cab Sender
2. Download DEV_UNLOCK.cab
3. Extract WP7 Update Cab Sender, goto “if needed install this tool”, install Setup-UpdateWP-x86 or Setup-UpdateWP-x64.
4. Copy DEV_UNLOCK.Cab into “WP7-Update-Cab-Sender” folder.
5. Launch WP7 Update Cab Sender.bat and choose S to send this package to device.
6. Let the HD2 reboot.
7. Your HD2 is now unlocked and you can sideload any apps in xap format into your HD2 Windows Phone 7.5 Mango.