how is the network build up via switch ? coaxial or twisted pair ?
what happens if you disconnect one PC and connect the one that it not able to "join"

Hi, Windows XP Pro is limited to 10 simultaneous connections to ohter systems. This is a hard limit and can´t be bypassed. If you need more than 10 connections you are forced to use a Windows Server version, which doesn´t have this limit. Some Information about this problem can be found in this MS KB article: http://support.microsoft.com/kb/328459/en-us

or use the fix
search for this
EvID4226Patch.exe
if you dont find it, pm me or something and ill mail you...
you can choose max ocnnections there...
but i dont think its connected

I fear the EvID4226Patch.exe won´t work as a solution for this Problem. Event ID 4226 is something that happens when Windows has reached the maximum number of half-open connections to other systems. This Event isn´t new, but Microsoft changed the maximum number of half-open connections to another sytem with SP 2 for Win XP. This is not the kind of connection which is established when you access a file or print share in a Windows workgroup (this kind of connection is called a session). Win XP Pro only supports 10 sessions at the same time, this is hard coded into the Windows XP Server service and can´t be bypassed afaik. The EventID 4226 is something that happens if an application tries to open more than 10 TCPIP connections to other hosts. The difference is, that these connections are used by the application and not by the Windows Server service. The Patch will help you if you have problems with filesharing apps, but it can´t bypass the hardcoded limit in the Windows Server service. I hope the difference is understandable

edit: fixed some typos

Ah, ho well, i was cute and thought i might help :}
well, if what he sais is true, than your screwed ; ho well, go linux :P

Delphi is indeed correct and yeah I would go linux too. ;)