The unofficial Windows 8 Beta blog posted a news story that Dark Forces Team released a Custom ROM Mango Build for HTC’s first generation Windows Phones

Now just a few days later we have a Custom ROM Mango Build (7713 build) which is at the moment only supported for the HTC’s First Generation Windows Phones like HTC 7 Mozart ,HTC surround ,HTC Trophy,HTC 7 Pro WMPU reports .

So if you are willing to risk the Warranty for trying out this beta Mango ROM onto your Windows Phones Head over to XDA Forums.I would personally not recommend to do so,since the official update is right around the corner

  DFT Releases Mango Custom ROM for HTC Windows Phones