A while back we mentioned that Firefox was working on getting a Windows 8 Metro Modern User Interface prototype going. There are some ‘internal builds’ that have been completed, but so far no Alpha or Beta release. This topic came up on Sunday in the Firefox Build forums today as a beta users was looking for the Windows 8 builds of Firefox and then also trying to get the Windows 8 Metro Modern UI of IE10 working. Turns out in Windows 8 you can only have one browser using the Modern UI in Windows 8. Further, this browser needs to be your…