The Official release of Windows Phone 7.5 (Mango) for HTC is not yet announced. We are expecting the official release sometime later this month. However, someone at xda-devs has already got hold of this soon-to-be-released ROM. The Windows Phone 7.5 ROM for the HTC Mozart handset has been leaked. You can download this leak from XDA-Developers forum.
The ROM will upgrade the European HTC 7 Mozart to build 7720 (the final version) of Windows Phone 7.5 ‘Mango’ . More details about this upgrade can be found at windowsphonereview