Open winamp, press Ctrl+P to open the Preferences window.
Find the option Global Hotkeys. Enable them if they werent enabled before.
Select the action from the drop-down list.
Click with the mouse on the Hotkey box and press the multi-media button.
Click on "
Add"
Add your keys one by one.

Note: You don't need to use the default combinations, so you can delete them all. I use a set of Ctrl+Shift+F_ buttons, plus a play/pause button that my keyboard has.