Don't worry ,it handles both 64 and 32 bit.
you will notice in your program files there will be 2 seperate ones

A Program files (x86) <-- 32 bit applications
and a Ordinary Program Files <-- 64 bit applications

Your computer automatically sorts them to the appropriate directory and handles it. Nothing to worry about. One of the advantages of 64 bit is you can use more then 4gb of ram. Hence its good to upgrade.
Of course there are other advantages too, but that just seems most worth while.

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