You can Unlock it simple by using the Unlock code,You can get the Unlock code and instructions at here
Theunlockarena and Unlock it...You can follow the instructions below and Enter the code
HTC Touch HD Unlocking Instructions
Warning : Do not enter any wrong unlock codes on your HTC Touch HD mobile phones. If you enter over a certain amount of wrong unlock codes on your HTC Touch HD mobile phone, your phone may get hard locked and sometimes become unusable.
1. Switch ON your HTC Touch HD with a
Not ACCEPTED SIM Card.
2. If your HTC Touch HD asks for a PIN code, then enter your SIM card PIN and press OK.
3. HTC Touch HD will ask to enter an "unlock code".
4. Enter Unlock Code we send to you.
5. Your HTC Touch HD is now unlocked.
*NOT ACCEPTED : We mean, to use a Sim card from a network other than the network your HTC Touch HD is locked to.