<<< In My Network Places/Entire network, microsoft windows network has a padlock on it, >>>
Are you sure that isn't the normal icon of a globe with a mouse superimposed on it? It could be mistaken for a padlock, but I've never seen or heard of the network being 'locked' with a padlock icon.
The claptrap that Windows displays about nobody having permission to do anything is a generic message displayed whenever there is a problem accessing another computer in the network. It is misleading and frequently quite incorrect.
Check that you have set at least one folder as "shared" in each PC by right clicking it and selecting the Sharing & Security option.
If the "remote" PC you are trying to access is running XP Pro, you may need to have a User Account set up with a Username/Password which matches that of the "local" PC you are using. More about this at click here
Any firewall software should be configured correctly to allow access to the local network traffic. Disabling firewalls doesn't always shut down the program's engine which may still be running in the background.