This is more than a bit out of place on HN in my experience, please, try to engage politely.
I’m not sure what I can say that will qualify as more than “nuh uh” to you, shy of getting a Core 2 Duo running with XP and the same keyboard as OP. That isn’t possible at the moment, is there anything else I could do?
300ms is a lot of time, especially if the calculator.exe was in disk cache already.
I admit you got me mildly anmoyed with the sports nonsense, sorry about that.
Anyway, you're talking about reaction time, which isn't actually relevant. The time between an action (pressing a button, or flipping a switch) and seeing the result happen isn't the same as the time it takes you to re-act to that something. Flip a light switch, does the light turn off instantly, or does it take a full third of a second? I guarantee you can tell the difference. 300ms of latency is actually huge and easily perceptible, even if it's faster than you can react.