Security permissions and file sharing problems!! HELP!!?

1. Four computers, all running XP Pro/SP3.

2. All stations on same workgroup

3. Simple file sharing turned OFF on all stations

4. Can see all stations in workgroup

5. Cannot access each other in browser; error msg: "\\(name) is not accessible. You might not have permission to use this network resource..."

6. I AM the administrator and logged on as such at each station

7. Using Westell 327W router via Verizon DSL

8. Two stations connecting via ethernet cable, two via wireless

9. Guest accounts turned OFF on all stations

10. All can ping each other.

11. Windows firewall turned OFF on all stations

12. All stations running McAfee Anti-virus, configured for file-sharing

13. In sharing/security tab, cannot see other computers to manipulate permissions

14. NetBIOS over TCP/IP enabled on all stations

15. Internet connection works on all stations

16. All users have unique accounts at each station

17. Each user's login/password is identical at each station (but not to each other, of course)

18. "Routing and remote access" disabled on all stations

19. IP Addresses are dynamically assigned. I couldn't figure out how to assign static addresses (or to disable DHCP) on my router.

20. Station #1 to #2, #3, #4: OK

21. #2 to #1, #4: asks for a login and password ()

22. #2 to #3: Access denied to folder (although I can see it in the workgroup).

23. #3 to #1, #4: OK

24. #3 to #2: Access denied to folder (although I can see it in the workgroup).

25. #4 to #1, #3: OK

26. #4 to #2: Access denied to folder (although I can see it in the workgroup).

27. I tried going into sharing and security for the folder I'm trying to share on #2 and I can't see other locations to add specific permissions.

28. Printer sharing works fine...