I have 5 machines in an office network. Two are in a "public" workgroup and three are in the private workgroup. I want to be able to prevent a user in the public workgroup from accessing or even seeing any folders and files in the private workgroup computers. Further, if I could lock out all public users from accessing Windows Explorer on the public machines it would be even better. I am not very knowledgeable in networking so you are dealing with a neophyte. Any assistance greatly appreciated

You protect file access via ntfs permissions.. There are a few ways to help secure systems. Personally I suggest that you get the junkiest oldest computer than doesn't connect to the local lan and let people play with it. Better still let them boot from a knoppix disk and take out the hard drive. Then lock down the lan computers too. I read it wrong and answer it wrong too. So get off my case you peanut.

"I want to be able to prevent a user in the public workgroup from accessing or even seeing any folders and files in the private workgroup computers." Answer: load ZoneAlarm [free download]and configure it on each of the three private pcs to deny access via the public pcs by host name. You can do the same with the Microsoft software firewall. This will secure the private pcs completely from the public ones. "I could lock out all public users from accessing Windows Explorer on the public machines" Answer: Since the desktop is explorer I don't see anyway of doing this. If you meant iexplorer you can use poledit [policy editor] on each public pc to disable ie. Use with extreme care or get someone more knowledgable on local policies to do the editing. Imagine the power if you knew how to internet search