I have booked my Win7 PC in tomorrow for a RAM upgrade (from 4GB to 8) ! They said they need to order it in because the part is different for many PC’s. Then they can get next day delivery. Its definitely worth a try as it could be (as you suggest) the cheapest cure.
I am not sure if I need to upgrade my Win8 as its on 8GB and seems to be ok. Is 16GB the next stage, or can you upgrade midway to 12?