First of all if it is for your wife and it is dog slow, you will hear about it. I speak from experience. If it is performance that you would not be happy with then why pass that system off to her. 16 GB of RAM will make a huge difference in performance. And if you really want to improve the response of the system then replace the HDD with an SSD. An SSD around 250-500 GB is not expensive and will really help with overall operation.
I picked up this computer from a resale shop, installed a new HD and battery, and was able to install Windows 10, running driver updates directly from Dell (read about some install issues on other boards), but it's running super slow. Crazy slow. Something is wrong slow.  In system performance, I'm seeing only 2 Gig of memory, used all the way up to 98%ish, and weirdly the C drive use up to 100%. I'm not a Luddite, but I am rather nube-ish at computer repair. Is it worth picking up two new RAM to upgrade this, or is there something stupid I'm missing? I was looking at two Hynix 8GB 2Rx8 DDR3L-1600 SODIMM - 896ms-896-H from Memory Stock for around $90 bucks. But I don't want to flush more money down a hole. p.s.: Computer is for wife, who uses is just to surf videos, write email, that type of thing. A home use, basher laptop. Ideas?
Is Latitude E6540 worthy of a RAM upgrade?