You have a lot of reading to do.

If you want to use https you will need to purchase a certificate, and unless you want to make your own life excessively complex you would then use IIS to create the initial website, and you could use ASPX to then make the web folder sharing ability.

Most of the web sharing thing doesnt work as a windows folder, it works more in the lines of a database of files - or it can work with a folder structure - but, you handle all the user authentification and settings yourself via a db.

So, it should not be a Server / Client software?
The sharing folders will be the regular folders that on the computer. how do I manage it's permission and sharing between computers - over the internet.
What about creating / editing files?

Thanks, Gil.

If you want a web front end, then it wont be client software - the web browser handles it all, otherwise you're just making effort for yourself.

I believe I covered the rest in my first post.

So,

How to implement this sharing?
The data those not keep on the server,
So how to I manage the sharing of it's folders & files, and sync them with other computer..?
The client will have a software,
Is this software will need to connect to the DB of the program and to update any change within the sharing folder?
Can it do that?
Or I should do that in a different way?
Thanks, Gil

first thing Id ask is why reinvent the wheel when theres a bunch of stuff to already do it, and you clearly dont know where to start.

I got a PM from b007 saying this is his school project.

so b007, other than I dont like people who PM me to try and get me to help them more than I already was, read the stickies, we wont do it for you and if you picked this as your project, ask your professor a lot of the questions.. As it seems you are stuck on design.