I am going to assume that you can see the machine when you browse the network from Windows explorer and all machines are XP/Windows 2000. If you cant see them, then there may be other issues.
So the issue here is Windows Networking. I won't get into the blah blah blah about it but its based on accounts and something called pass through authentication. When you try to attach/use a resource, your machine tries the currently logged on user to attach to the machine. If that user is not a part of the machine that you are trying to access, then you will get Access Denied.
So if you are logged on as user 123abc on computer1, then user 123abc needs to exist on computer2 and have rights (which you seem to know about) to the share. To create accounts, you have to be an admin on the machine. Use the Adminitrative Tools control panel applet to Manage the Computer (Manage Computer). Click on Local Users and Groups. Right Click on Users to add a New... account.
There is a group called everyone that you can use, but it is soooooooo dangerouse that I dont reccommend using it. Basically it give Everyone, and I mean EVERYONE, access to your machine from the your local ISP and the Internet. Most ISPs block the traffic for MS networking at their borders, but not within their borders. So if you have a cable modem, you will be sharing that resource with all the other subscribers of your cable network.
Unsolved 
