If you share your Mac folder with 'Everyone' and it still isn't working, be sure that the 'Everyone' account has the right to access shared folders. To check this:
1) Click the Apple and then System Preferences
2) Click Accounts
3) Click the lock to unlock the sheet so you can make changes.
4) Enter your password
5) Click on the 'Guest Account' and ensure that 'Allow guests to connect to shared folders' is checked.