Go to control panel, pick keyboard. If you have a Key setting tab then you can reprogram it. If you have the key setting tab, pick the icon that matches one of your buttons. Click edit and a modify key behavior pop up will appear, now pick "Start a program" then click next. Now put in the link of the program that you want the keyboard button to open, example "C:\Program Files\LR Cool\Virtual Dub\VirtualDub.exe".
Good luck.