I believe nothing is secure. Even you have the safest OS in the world, if you gave your private keys then security is pointless.
True, but don't just give away your private keys. Do what you can to protect it, it's your money.
I actually use windows XP even outdated I feel secured because I don't keep my keys around.
You have to upgrade somehow though like they said this depends on how you use your browser and your habit with what you download.
Does hackers are still scouting on older version of windows?