so here are the links to the ram that i have. the samsung one was origianally istalled when i bought the laptop and it had 2 of them, since my laptop can handle 8 gb of ram. its a hp probook 4540s.
one of the original ram
Samsung original 4GB, 204-pin SODIMM, DDR3 PC3L-12800, ram memory module for laptop ( M471B5173EB0-YK0 ) at Amazon.com
replacement ram
PNY MN4GSD31600-Z 4GB DDR3-1600 PC3-12800 CL11 Notebook Memory Module MN4GSD31600-Z - Micro Center
Just as I thought.
You have mismatched ram modules.
You need to get a 2 module matched set.
Jack
In theory any compatible RAM modules should work together but things don't always work that way in the real world. Any difference in specs, size, or even manufacturer can cause problems. OEM computers such as laptops tend to be more picky about the RAM modules that will work. The only real solution is to use matched modules.
I believe the installed RAM size comes from a simple identification of the RAM modules. This doesn't imply the memory is usable or even fully compatible, merely that it can be identified. The value for total memory comes from a test of what is actually usable. The difference is labeled as hardware reserved. It will never be zero is usually quite small in a 64 bit OS.
Don't be concerned about a low value for free memory. It should be low, zero being the optimum value. Windows was designed to work this way. The important number is available memory and you have quite a bit of that, and there will be more when the RAM problem is corrected.
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