There are a number to utilities that can do what you ask. I would recommend AutoHotkey. Most of those extra keys have documented functions which can be remapped. For the rest you may need to do some work to find the keycodes generated and then you can map them as you want.
Here is a list of known special keys on my installed copy AutoHotKey,
Browser_Back Back
Browser_Forward Forward
Browser_Refresh Refresh
Browser_Stop Stop
Browser_Search Search
Browser_Favorites Favorites
Browser_Home Homepage
Volume_Mute Mute the volume
Volume_Down Lower the volume
Volume_Up Increase the volume
Media_Next Next Track
Media_Prev Previous Track
Media_Stop Stop
Media_Play_Pause Play/Pause
Launch_Mail Launch default e-mail program
Launch_Media Launch default media player
Launch_App1 Launch My Computer
Launch_App2 Launch Calculator
For the rest, you can use the command #UseHook on in the script file to then be able to see the key codes generated by pressing the special buttons.
https://autohotkey.com/board/topic/64875-mapping-special-keys/ for a related discussion and information. More here, https://autohotkey.com/board/topic/64503-make-the-fn-key-usable/