how to upgrade 32 bit (86x) to 64 bit (64x)?

I want to upgrade my 32 bit system to 64 bit, I have (4 GB ram), graphic card (512 ati radeon 5450). System Intel (core 2 duo E6550). If any things require to buy I will buy it such as (processor ,, ram,, graphic card,, )..
I just want to play high graphic games...
Sorry for wrong English...

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