Eu encontrei isto:
In HKEY_CURRENT_USER\Control Panel\Keyboard the values KeyboardDelay and KeyboardSpeed control how long you hold a key before repeating starts and how fast the repeat rate is when it does start. The former ranges from 0 to 3, the latter from 0 to 31. BUT I'm pretty sure Windows won't accept a rate past 31 and of course the delay can't be less than 0.
The key HKEY_CURRENT_USER\Control Panel\Accessibility\Keyboard Response may prove to be more useful. The user reports good results from these values:
"AutoRepeatDelay"="200" "AutoRepeatRate"="15" "BounceTime"="0" "DelayBeforeAcceptance"="6" "Flags"="59"