Just bought a T420 i5 2520M with 4 GB Ram. I know from your post this laptop takes 8GB dimms. Can I use only one of the following with existing 4GB I have, to make it 12 GB. Found this on Amazon. Kingston Technology 8GB (1x8 GB) 1333MHz DDR3 PC3 10600 204-Pin SODIMM Memory KTA-MB1333/8G by Kingston ...