If they thought the Mac did not support SMB, they were wrong.
For you to access a windows network, you'll have to turn on SMB and you may have to specify the workgroup. Just go to Directory Access, which is in Applications-->Utilities, and click the box next to SMB/CFS to turn it on. Click configure and you can specify a workgroup name to join. I think the default name is "workgroup" but I don't remember.
To allow others to mount a share from your computer, just go to System Prefs-->Sharing and look on the Services tab, where you'll see "windows sharing". If you turn it on, your Mac should be recognized by the network. For you to mount network drives, you just go to the finder, and you may be surprised to find network shares by clicking on network in the sidebar. Or you might just hit command-K (or Connect to Server from the Go menu), and either browse to find a share, or specify the ip address directly.
I hope I got that right -- I really ought to be sleeping....
Mark