I hope Phill will forgive me for "chipping in" with my 2 penn'orth
Second hand RAM can be OK..... just like a second hand car can be OK.... RAM modules are susceptible to damage by static electricity...
1 If you buy second hand RAM you have no way of knowing how it has been handled by its previous owner....
2 Were full and proper anti static precautions, taken? ( both on removal and replacement)
3 How was the RAM module stored when it was not in the machine? (Correctly in its own anti static and protective case? or just shoved in a desk drawer with other stuff?)
4 How do you know the RAM was compatible with the previous machine it was installed in?
5 Has an over voltage ever been applied to it in a previous machine and if so how do you tell what latent damage has been caused?
6 Has there ever been any liquid ingress into the machine(s) it was installed in? ( despite careful cleaning electronics often fail around 9 to 12 months after the liquid ingress, quicker if the liquid is not pure water, for example coffee, tea, soft drinks, wine etc.)
7 Is your computer capable of using faster or more RAM? (If your Mobo or OS can't handle it, there's no point in fitting it.)
8 Why is the existing owner getting rid of it?
These are the sort of thoughts that might spring into my mind when purchasing RAM, and remember whilst there are no moving parts in the usual RAM module RAM sometimes does just go bad, as the memory chips are not everlasting!
Personally I always recommend my customers visit the crucial.com website, run the Crucial scanner, get the details of compatible RAM and purchase from them accordingly.( with their guarantee).. However as always it's your machine so it's your call, but do calculate most carefully, the likely saving in price between new and used RAM modules, with the attendant advantages and disadvantages.