If you go into Control Panel, there is an option on XP to specify what sounds are played for an event, you can google 'you've got mail+wav' and download the file and then select it in the above menu, it might depend on what e client you are running though
It depends on how you access you mail, e.g. through a client (Outlook, Thuderbird, etc.) or through the web (using Internet Explorer, Firefox, etc.). If you clarify this maybe someone will provide the details.
Thanks for replies, however I have decided based on those that it is far too complicated ( I don't even understand your questions!) ...am only a fledgling when it comes to the computer, I'm afraid.