The way I've previously accessed content files is by setting them to "Copy always/if newer", then loading the file directly.
However, browsing the web, it seems there's another way to load it - That it's automatically included in the .exe/.dll. However, I've been unable to find out what the method is, to access said included content.
It is Embedded Resource
. This will cause it to be streamed into your assembly.
Here is Microsoft's walk thru: http://support.microsoft.com/kb/319292