Done this before, hopefully I can remember everything, here goes...
You need to go to Network & Sharing Center on all computers and enable, File & Printer Sharing, Folder Sharing ETC.
Set your network on each system to a Home Network, Public not Private. Then you need to setup file and folder sharing for any other file/ folder which you want to share (which isn't already in the shared documents file)
Then on each computer go to My Computer, and Map Network Drive. Select your drive from a list and the Drive Letter and you're done.
NB: Antivirus Programs have a massive effect on file sharing, so add any computers to your exception list.
NB: All the computers need to be in the same workgroup!
If you get stuck give me a shout, I still use VISTA but done this for my Windows 7 Laptops as well.