
Beginning March 29, 2010, HD7 users will start to receive a a pop notification on their HTC HD7 device, informing them that a software update is available. Before beginning the update process, please be advised of the following:
The update is a two part update.
See HD7 Software Update - What's included for more details.
The update must be done using MIcrosoft's Zune software.
Each part of the update will take approximately 20-50 minutes to complete.
Important: The total time to complete the update is primarily based on your internet connection speed and the amount of data currently on the phone.
Zune will automatically backup and restore all user settings and device data.
DO NOT disconnect the device while the update is in progress
If the update fails, the device will revert back to the last software version that was successfully installed
To complete the two part update, you will need to follow the below steps:
1. You will receive the following notfication when your device is ready to receive an update.

2. Connect the device to a computer using the USB cable inclued in the box.
Zune should automatically open once the device is connected.
If you do not have Zune installed on the computer, a pop-up should prompt you to download and install it.
See HOW TO: Install Zune desktop software for more details.
3. Wait for Zune to finish checking for updates.

Full instructions, see T-Mobile website
http://forums.t-mobile.com/t5/HTC-HD7-Knowledge-Base/HOW-TO-Update-the-HTC-HD7-to-the-Latest-Software-Version/ta-p/802003