The reason that I get confused, is that I can log on to certain people's folders (I am alone in my household) and not having to enter passwords.
As cybercore has explained other computers that are on wireless networks, within the range of your wireless network card may be viewable and even accessable by you if they are not secure.
If the above quote is true then I'm not sure why you have created any shares, with or without passwords, however; you should as a matter of best practices protect your entire I.T. infrastructure with unique usernames as passwords. These should be unique, known only by you and exist at every level. Unfortunately defaults are defaults and not intended for long term use.
Wireless networks have something called SSIDs which they broadcast to advertise their existence and availability. Adjust your SSID by using the web interface on your router make it uniquely your own or perhaps choose not to broadcast it at all, your option. (Read the manual for your specific make and model)
Wireless networks use encryption (not always by default) you've said that you have a difficult password, I can only recommend using the highest level of encryption support by all wireless devices on your network, WEP may look difficult to crack to you and me, but trust me it's not, investigate using WPA or WPA2 if supported. (Read the manual for your specific make and model)
Your computer should be protected by a unique username and password (at logon) passwords are case sensitive so a simple password containing special characters as well as alpha numeric characters like P@$$w0rd are generally accepted as best practice. Make sure that the "Guest Account" is disabled. Shares should be protected as strictly as possible, accessable only by specific users with passwords created according to best practices. The everyone group generally should not be used and I would suggest, if you are concerned about security (as you should be), that you revisit each share, right click and from the share with option, choose either nobody, or a specific user.
Workgroup names should be unique. So make it your own and don't use default settings like workgroup or mshome, just make sure that all of your network nodes have the same workgroup name. You can change your workgroup name as well as your computer name if you wish by right clicking "Computer" choosing properties and on the resultant system page, choose the link that says "Change settings".
Perhaps if you would type the word network into the search box and then choose it ("Network") from the resultant menu and use the "Snipping Tool", you can create an image which you can then attach to your next post, inorder so that we can better understand your specific issues.