How can you tell if Memory (RAM) is bad when Computer Properties says 8.00 Gb RAM present but only 3.25 usable.

Ordered several sticks of RAM from a well known province through the AliExpress group. Paid like $40-$50 for it. When I got it I noticed that my Windows 7 Pro machines actually are working slower. Could this be bad RAM. It would appear that all of it is bad. The manufacturer says Crucial a reputable company. I have had many. of their products with no problems. Now looking at the Properties of my Computers. I have two windows machines that have the Adobe Master Suite collection and several others like QuickBooks. It is like why be driven by the force of the market to keep upgrading when what you have works well. Well when I wanted ot increase the memory on these two machines from 4 to 8 GB Ram I thought I was getting the deal. From what I can tell the RAM is being recognized as on board but not registering as USABLE? From the screen show. I have the one here and another that says 8.00 GB RAM with 3.25 usable. Does that mean that the 4 extra sticks I bought are bad. How can I tell if it is good or bad?
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