The first step is: Start > My Documents
So you have the My documents folder open.
Second click the tools button, than select folder options.
Now you will see a few tabs, we want the View tab so go ahead and select that one.
Now scroll down the list and double-check that "Use simple file sharing (recommended)" setting was checked.
Click the OK button
Open a new folder in My documents
Next right click on the folder and select Properties.
Choose the Sharing Tab
Double check that the "make this folder private" option is not checked
Click ok and close the properties window and now drag the folder you would liek to share to the "Shared Documents" folder located on the left hand menu.
Now right click on the Shared Files folder and select properties, choose the sharing tab
Check the box beisde the dialog "Share this folder on the network"
Now all computer connected to your workgroup or domian can access the folder, that you wanted to share.
Now for confirmation there should be a little hand holding your folder, you are sharing.