Worst case scenario they won't mix well together and the PC won't boot so you have to remove the second set. Best case they work fine down-clocked to the lowest common denominator.  In between is BSOD and random restarts/freezes.  Disable XMP in BIOS before you try booting with 4 mismatched sticks. By itself, adding RAM won't damage the PC.  You of course run the risk inherent in any upgrade of user damage like static discharge.  
Hi!, Can you mix two types of Dell OEM memory into one computer? In my case, I own two Alienwares A11!!     and I would like to transfer my two 8Gb sticks [NAME] (XMP) from one computer into the other one which has already two 16Gb sticks [NAME] (XMP), so that I now would have 48Gbs into that second one. The specs of the memory sticks are almost the same but there are slight differences, and I don't know if they matter or not:   Kit 1: (XJ69DF-MIE2 is being reported by HwINFO) 370-ADUH : 16GB Dual Channel HyperX(FM) FURY DDR4 XMP at 2933MHzJ69DF 8GB HyperX Fury XMP DDR4, 2933MHz, 1Gx64, Unbuffered, 288 pin, Single Rank, 1.35V, Non-ECC, Kingston XJ69DF-HYA/XJ69DF-MIE/XJ69DF-MIE2   Kit 2: (XRMWRN-MIE2 being reported by HwINFO) 370-ADWK : 32GB Dual Channel HyperX(FM) FURY DDR4 XMP at 2933MHzRMWRN 16GB HyperX Fury XMP DDR4, 2933MHz, 2Gx64, Unbuffered, 288 pin, Dual Rank, 1.35V, Non-ECC, Kingston XRMWRN-HYA/XRMWRN-MIE/XRMWRN-MIE2   Can someone tell me if those 1Gx64 vs 2G64 and Single vs Dual rank differences matter or not? Can I safely transfer my sticks?   Thank you!  
Aurora 11, Mixing two types of OEM memory running at the same speed