To unlock a HTC Touch HD you must remove the SIM lock with an unlock code. An unlocked HTC Touch HD will allow you to use your HTC phone with any phone carrier network. The free unlocking instructions below will simply help remove the SIM lock that is enabled on any SIM or GSM based HTC phone by default.
There are many ways to get an unlock code for your HTC Touch HD, but I would suggest calling up your phone carrier first and requesting one for free. They will request your Touch HD’s IMEI number in exhcange which you can find by typing *#06#. If you are unable to attain a free unlock code this way, you could also try paying for one from an online vendor. However, they will probably give you the same unlocking instructions below that I am providing free. Make sure you are just getting an unlock code, as some services will try and sell you the instructions as well. You can find out how to unlock most HTC phone from this article, which the instructions below are based off of.
Unlock SIM on HTC Touch HD for free
1. Power on your HTC phone with an unaccepted SIM card in (or no SIM card at all).
2. Enter your 8-digit unlock code you attained earlier.
3. Your HTC phone should be unlocked and may automatically reboot!