Eh...actually it is. First off, check your Network control panel settings. You should have the service installed at the bottom that says "File and Printer Sharing for Microsoft Networks". If not, add it.

Next, you'll have to reboot your computer. After that, right-click on the folder you want to share, select "Sharing..." and add a new fileshare. It'll now be visible in your computer on your workgroup browsing through Network Neighborhood. Or...if you felt so inclined, you could access it in an address bar (Or the Run command) by typing \\COMPUTERNAME\FILESHARENAME.

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"And knowing is half the battle!"