your processor does support 64 bit OS.. however, even though the ram upgrade can be done i dont think it will do you any good..if you observe, your computer will hardly every utilize the full 4 GB of RAM, let alone 8 gb... your processor supports 64 bit for the sake of it.. even if you upgrade to 8 gb ram, you will first of all have to open up a lot of applications to utilize the ram. (atleast 5 to 6 heavy load programs) and if you do that, your processor wont cope up anyway..
and if you dont use so many applications, then even the most processing and graphic intensive games that you can probably play on your comp. wont even eat up more than 1 gb of ram at a time at any given point of time.
i dont think upgrading the ram more than 4 gb is gonna do you any good.. rather spend that money elsewhere.. .
even processing intensive 3D applications like Autodesk Maya which i use, uses about 350 MB of Ram under normal conditions and goes up to not more than 500 to 600 mb at any time even when it is running on full capacity rendering and churning the processor at 100% continuously for more than 2 hours..
windows 7 wont use more than 1 gb for itself, even if you consider that each other app. of yours uses 1 gb of ram all the time, you need to run 7 such applications to fully use the 8 gb of ram, and if you do that, your processor will give up...
and the above spec. you have given is of your processor. What RAM you can use, how much u can use, and what frequency you can use, whether you can use DDR2 or DDR3 or higher depends on your motherboard..
Plz mention which motherboard you have if you finally want to upgrade your RAM anyway..