The minimum requirement for system RAM (system memory) for Ethan Carter listed at
***Game-Debate*** is 2GB, not 4GB, but that may only be for XP and not later versions of Windows. 4GB is the "Recommended" amount. Steam and GOG both list 4GB on their respective webpages for the game.
http://www.gog.com/game/the_vanishing_of_ethan_carterhttp://store.steampowered.com/app/258520/I suspect that the game originally listed minimum requirements at 2GB of system memory, but they never tested the full game with that amount -- and later they realized there were parts of the game where it needed more than 2GB. Although there are reports of people playing the game successfully with only 2GB of system memory, those people may have optimized their computers by closing down all background programs.
Adding memory to a desktop computer isn't that difficult as long as the motherboard supports 4GB or more, but you need a 64-bit version of Windows to make use of 4GB or more. If you have a 32-bit version of Windows, you wan't be able to make use of more than around 3.25GB or at most around 3.5GB of the memory, depending on the computer's motherboard.
You never mentioned whether you have a 32-bit version of Windows or not. But if you have a 64-bit version of Windows, you might consider adding more system memory so you can play the game -- especially if you were able to buy the game at a discount.