64 over 32 bit Windows 7 is 64 bit can use over 4gb of ram. Being able to access more memory helps with performance. Most PC available in retail now come with 4,8 or 16 gb of ram and some gaming machines can be configured with 32 or 64 gb of ram. It's not necessary to have that much memory but if you do anything over 3.2 or so GB's is wasted.
what i need to make it 64bit?

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