I'm sorry, I got this all wrong.
Maybe I'll get it right this time: Mouse Hover Time - Change
Open regedit and go to HKEY_CURRENT_USER\Control Panel\Mouse, then change MouseHoverTime to whatever you desire. You'll probably need to log off and back on for it to take effect.
Edit: Oh, and the other value you changed is the desktop preview when you hover the little box on the far right of your taskbar. You may want to change that back.