after upgrading RAM my pc keeps on beeping, HELP!

[Lars1999vk]

after i tried to upgrade my pc from 4gb to 8 gb ram my pc keeps on beeping and the screen wont turn on. if i put the old stick back in there it works fine, also if i put both in there it starts upo fine but only recognizes the 4 gb stick. i am kind of a noob in this and dont know what the problem could be. i checked if i had all the required, ddr3 same dimm and my motherbord should be able to run the 1,5volts (says the medion person i asked atleast). my pc was a prebuild so im not sure what is all in it. the new ram stick is a ddr3 8gb HYPERX by kingston.
Pls help me.

 

[ak47jar3d]

This is a very common issue with ram. Mix and matching ram creates incompatibility. You should only mix ram that come in the same retail package.