Board Thread:Questions and Answers/@comment-11541060-20130705020356/@comment-11699684-20130714102435

When you create a world in Minecraft, the world file itself is saved individually from the Minecraft .jar. I believe you have to find the individual world. Have a look through %appdata% (enter that into start menu, you should know that but just in case). Then Zip file the world and upload it to somewhere like Planet Minecraft or just email it to them as an attachment.

If that doesn't work, then I'm not sure!