The iMac can certainly be added to the network.

What kind of network is it? Wired or wireless? If it's a wired network, just plug the iMac to an available ethernet port and mess with the settings in the Network System Pref.

If it's wireless, you'll need an Airport Extreme card for the iMac. It may already have one installed. Set up for wireless is just as easy. If you've configured the network for the PCs, you'll have no trouble getting the Mac on.

If you have any more problems, you'll need to talk specifics.

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