No one likes locked phones which restrict your activities to a certain carrier and do not allow you to install apps which are not in the available market place. And with the introduction of HTC HD2 by T-Mobile, which incidentally sold out in the first few hours, there might be several users who might be itching to unlock the phone and play around with it.
If you are looking to unlock the HTC HD2 you recently bought from T-Mobile, XDA Developers has released a HSPL2 which will allow you to flash the HTC HD2 and unlock it.
Once you unlock the device you can install apps or ROMs which are unofficially available. Instructions to download the HSPL2 and flash the HTC HD2 for T-Mobile is available on the XDA Developers site.
Please make sure to backup your device before you flash it. We take no responsibility if you brick your device, so continue with caution.
Important note: Using the HSPL2 on your device will void your warranty, so use it at your own risk.