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I upgraded the RAM from 2 GB to 4 GB by adding another 2 GB memory module. But, in system specs it shows as follows: Installed RAM 4.00 GB (2.84 GB usable) Why is only about half is usable and not full? Pls help me in fixing this problem

Depending on the OS your in the right ballpark if you are running 32 bit OS then the most you would get from the memory is 3.3gb and since you have a media accelerator on your graphics card it can use up to 1 gb of your remaining memory dragging your memory down to 2.3 or less when its running full out in a game or heavy video but during a simple task of checking the allotted memory it wont be using that much so theres were you have 2.8 usable at that moment. Another thing to check is that you matched the memory.The frequency, latency and timing they need to be the same to function properly. Hope this helps

32-bit something. By something, I mean your OS, chipset, or processor. If any one of those are 32-bit that’s the source. If your chipset is 32-bit your out of luck. If your processor is 32-bit, you might be in luck. If your OS is 32-bit, that’s easy. What is the model of your processor?

if you are using a 32 bit OS your ram wil be split it only uses half of the space available if yuo upgrade to a 64 bit OS it will use all the space

As mentioned in previous answers, 32-bit os limits to about 3.5~3.7gb RAM. If you have integrated graphics you also share the main 4gb RAM with the integrated graphics. If you want to switch to a 64-bit OS, it is actually quite simple. Download the ISO or create a USB bootable installer from Microsoft for free. You can use the key that was included with your laptop for activation.