While it is relatively straightforward to share a folder in Windows 7 (simply Right Click, then Share With...) a common issue arises if the shared folder is shared with 'HomeGroup'. The folder needs to be shared with a 'Specific Person...'. This is a very common occurrence in Windows 7 because the default behaviour is to share all folders with HomeGroup. This currently doesn't work with the stick because sharing with HomeGroup is only possible with other windows 7 machines, and the stick isn't windows 7.
1) To fix this, browse to the folder on the PC you wish to share, and right click
2) In the menu, select Share With...
3) Then be sure to select 'Specific People..."
4) A popup window will appear that says 'Choose people to share with'
5) Make sure at least one account is set under 'Name', and if you want to have this folder accessible without a username and password, click the arrow drop down and select the 'Everyone' account and click the 'Add' button.
6) Finally, click the Share button at the bottom, and the folder will be properly shared for use with the Wireless Media Stick.