how can i share my folder only for one person in my work group network?

Answer 1

In a workgroup network you cant do it. If a file or folder is shared then all can see it. In a domain network you can do this.

Answer 2

There are a few "work arounds" from standard security settings that will let you accomplish this. The most obvious would be for you to give your password to that person you trust with your life. In effect, you would be sharing or using a
"joint account" which would mean a shared user profile.
What an interesting idea! Another more practical approach would be to use a 3rd party program that can store and password protect any or all of your folder contents outside of Windows. There are other ways you might be able to "tweak" the security settings in the Windows registry, but this is only for the very advanced knowledgeable user (I'm not one of them). I think it would be best to get the security features that are in XP Professional, where you can share your folder with limited "read only" rights assigned with access given to whoever.