Its probably software package you need to install to enable those keys. You can probably contact Acer and find out exactly which one you need.
You can find the 3rd party software that shipped with the laptop available for download here:
http://www.acerpanam.commy guess is there might be a problem with XP since Acer probably shipped it with Vista and only supports that.
If an installer gives you a problem we can probably get around it, let us know.