It's true about the upgrade. I had only 4 GB RAM laptop. I've installed a 2GB card and it stopped being so slow. My laptop used lo lag when I opened several tabs and now everything's fine. I would never think the problem was in RAM. Andhow did you upgrade your laptop? As for wifi, it's true that microwaves and some other devices affect its performance. But it only true for 2.4 Ghz wifi. If you have 5Ghz, these devices won't interfere with its work. But then again, you'll have lesser range and signal penetration.