|You can't do both dhcp and static ip at the same time so all of this makes no sense|
"All is well if I use a set ip address range and all computers can see all others, share files etc. However to access broadband I enable automatic ip address on all 3 machines "
Confirm pc 3 has an ip address from your router. Make sure the dhcp scope in the router is providing more than two ips.
concerning the account name it has nothing to do with internet access. Didn't you rename the jim account to john? I don't believe a rename of an account changes the documents and settings name which is what you are seeing.