I'm attempting to set up a small office network capable of file and printer sharing. The main computer will have (has) direct connection to a DSL modem that doubles as a Wireless router to the other PCs I wish to be on the network. Do I need additional software to get anything out of this network other than a shared internet connection via the DLS modem?

*edit* I sort of figured it out on my own. Even though the Windows Networking Wizard claims that you cannot network them together in that fashion, you can. You need to manually set the work-group name on each machine to match. Doing this, they should recognize each other if you access them through "my network places" / "workgroup computers".

Note: Some of the terms might not be exact, but the general idea remains the same. Feel free to ask question if you need additional help.
lol this sounds like a question out of a text book
you tryin to get us to do your homework for u?
In response to Falacy
No, honest question. All computers can access the internet as intended, but they don't appear to be configured properly to setup a workgroup. That is, according to Windows Networking Wizard.
In response to Koshigia
Are they using different versions of Windows? I'm currently trying to do something similar, where one PC is XP and the other Win2000 and I'm having trouble accessing any resource from other computers.
In response to Hazman
The main computer is running XP Pro, as are two others. The fourth is using Vista.
In response to Koshigia
In XP, right click My Network Places and hit Properties, then right click the LAN connection and hit Properties. Check to see that "Client for Microsoft Networks" and "File and Printer Sharing for Microsoft Networks" are both there. These are installed by default, but somebody might've uninstalled them or selected not to install them. This is the only thing I can think of.
In response to Cinnom
They are already installed. I'm going to attempt to setup the network manually by sharing portions of the hard-drives and printers and see if they can be accessed