James, I don’t think your doing anything wrong. Its Micr$s$ft thats done it different in XP.
First off the XP reg hack is used to put Windows X Pro into a compatibility mode in some sense. Windows XP Pro is designed to be able to logon to only Windows 2000 and above domains. When the reg hack is done it allows XP Pro to logon to Window NT 4.0 domains. Since SAMBA emulates an NT 4.0 PDC you can see where the problem is.
RequireSignOrSeal Registry hack
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\netlogon\parameters
"RequireSignOrSeal"=dword:00000000
However this is not your problem at this point….. You should be able to join the Samba domain without making any changes to the registry. Its when you reboot the problems starts. The registry needs altering at this point or you will receive a trust account failure when attempting to logon.
As long as your able to join other machines to the domain, having Samba properly configured. Here’s what you should look for in Windows XP Pro.
-You need to make sure file and print sharing is checked off and that you are in fact sharing. Check the sharing on the hard drives and they should have admin shares C$ etc.
If not enable file sharing.
Where I think your problem stems from though is SFS. I have seen access denied errors when it is enabled. Here’s an explanation write from a book.
-Simple File Sharing (SFS), which allows less technically inclined users to share files with less risk. Directories like Windows, Program Files, and the Administrative shares are inaccessible when SFS is active. SFS also prevents granular security administration, so a share is either used by everyone or no one.
To shut down SFS, I select Start | Control Panel | Switch To Classic View | Folder Options | View, uncheck the Use Simple File Sharing option at the bottom of the list, and click Apply.
Now you should be able to join the domain… let me
Jason