Right Click on the folder to be shared
Select Sharing and Security
Check the box Share this folder on the network
When the security warning comes up just share the folder anyway.
When you look for the computer by IP address from another machine you should be able to see the folder.
If you check the box to allow network users to change the files they should have full read write access to the files.
This proces is very different from service pack 1 or 2. Much Simpler, much less controllable.