A correction to my earlier post. Windows Live Mail 2012
can be used with Windows 8 and, given that the web has thousands of posts from people saying that Windows 8 Mail is totally useless (especially when trying to send attachments, as you are), it's probably the best way to go.
Download and install Windows Live Essentials (which includes Windows Live Mail 2012) from here:
http://windows.microsoft.com/en-gb/windows-live/essentials
Then open Windows Live Mail. It will hopefully ask if you want to use it as your default email program. (Rather obviously), select 'Yes'.
If you don't get offered the option to set Windows Live Mail as your default program, try my original instructions again (because the presence of Windows Live Mail may have made 'MAIL TO' an available option).