For those using 64 bit version of Windows 7, Mozilla has some good news. Mozilla has started offering 64 bit builds of Firefox nightlies for Windows as well.
But since not all plugins like Java and Flash are available in 64 bit versions, you need to run 32 bit versions of the plugins. You can grab the 64 bit builds for the Firefox trunk here.
After installing the Firefox 64 bit build more than likely you will see a missing DLL (MSVCR100.dll) error while starting Firefox.
This can be fixed by installing the Microsoft Visual C++ 2010 Redistributable Package from Microsoft. Once that is done, just look at your about screen of Firefox Win 64 bit build.
Source – Mozilla Links
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