Cannot connect to computer on WinXP network

I am having a little bit of network difficulty here. There are 3 computers on the network I've set up here at the office. Two are running WinXP and one is running Win2K. We have a Linksys WRT54G router. From my boss's computer, I can connect to either of the two other computers like normal. I can copy files to and from the other two computers. The two other computers can connect to each other fine as well. However, if I try connecting to my boss's computer from either of the two other computers, I get an access denied(no permissions) error message. My computer and my boss's computer are both running TrendMicro PC-Cillin 2006 with windows firewall turned off. I have tried adding an exception to his firewall to allow my computer's IP address to connect. I have tried shutting off his firewall and my firewall altogether. All computers are in the same workgroup.

I saw in another forum that someone mentioned modifying the the HOSTS files on both computers but I am unsure how to do this or if it's even worth trying for my particular problem.

Any help or suggestions will be greatly appreciated.