Two options:
1. The RAM is defective
2. You bought the wrong RAM
I think the second is more likely than the first.
So go to www.crucial.com and tell their memory selector what it wants to know about your computer or motherboard (like make and model). It will tell you the type of RAM you need and you can even order it.
Kees
Hi... I just bought a new ram(http://www.public.gr/product/computers-and-software/anabathmisi/mnimes-desktop/kingston-hyperx-genesis-khx1600c9d3-4gb/prod1230026pp/) but my pc ain't recognise it ... If i join the stick with the old one(my pc has 2gb ram installed) the pc will start but the system says it runs with 2gb ram... If I put only the new ram, pc wont start.. Any ideas ?? I can give you any additional information you may need about my pc, but please explain me where i will find it.. I mean, if you want to know about the CPU tell me: "What CPU do you have..you can see it there bla bla bla .." Thnx for your time...

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