Many of the old 2GB machines ran a 32 bit OS so without debate, you have all the RAM you should have.
Let's hear more about this PC using this tool to pre-answer most questions save one. That one question is: What make, model Power Supply is in the case? This matters since its too old or small you get to replace that too.
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what changes should I do on my old pc in order to run high-end games?
my old pc has 2gb ram.no graphics card,dual-core processor.