I was browsing and came across Keyboard Cleaner, a mac app that "comes in handy when you want to clean your keyboard, but you are afraid you might trigger a command or change or delete some of your current work beyond repair and undo...It shields your desktop and intercepts every keystroke you might accidentally make — except for Command-Q"
I don't think I have seen a Windows equivalent. If there is no such tool (perhaps using AHK?) for windows it could be very useful.