Windows XP tries to sign or seal the secure channel between the workstation and the domain controller. This causes the following error:
Windows cannot connect to the domain either because the domain controller is down or otherwise unavailable or because your computer account was not found.
The domain controller may record:
Event ID: 5723
The session setup from the computer <Computername> failed to authenticate. The name of the account referenced in the security database is <Computername>. The following error occurred: Access is denied.
The client may record:
Event Source: NETLOGON Event ID: 3227 Description: The session setup to the Windows NT or Windows 2000 domain controller \\<!ServerName?> for the domain <!DomainName> failed because \\<!ServerName?> does not support signing or sealing the Netlogon session. Either upgrade the domain controller or set the !RequireSignOrSeal registry entry on this machine to 0.
Save the followig text to requiresignorseal.reg and then right click->Merge