win upgrade to 64-bit system on old Dell E5500

I own a Dell Latitude E5500 laptop running with a GE45 Express Chipset.  The processor is a Core 2 Duo T7250 (2.0GHz, 2M L2 cache, 800MHz FSB).  I have 2GB DDR2-800 SDRAM memory and running Windows Vista Business 32-bit operating system.  I would like to upgrade to a Windows 7 or 8.1 (or even 10) 64-bit system if I can. I’m going to upgrade my memory to 4GB to do this. Can anyone tell me if I have to stick with 800MHz and upgrade the processor?  What are my processor options if I go with that? Does the processor need to be 800MHz, too? Thanks.