trust domain win2k3 and win2k8

i have installed windows 2003 as domain controller hostname.a.com with exchange 2003 and another windows 2008 domain controller hostname.b.com with exchange 2007 seperate forest,,,, i need the following


1- trust domain between these two domain
2- migrate the users from windows 2003 to windows 2008
3- migrate the mailbox also

WHEN I TRY TO migrate the users using admt it is given (2008-01-17 13:56:13 Starting Account Replicator.
2008-01-17 13:56:15 ERR2:7816 Cannot determine if source object 'LDAP://DC1ayz.xyz.local/CN=GP,CN=Computers,DC=asg,DC=local' matches an object in the target forest or domain. The handle is invalid.
2008-01-17 13:56:15 ERR2:7301 Failed to migrate source object 'CN=GP' to domain 'abc.com'. The target object could not be created. hr=0x80070006 The handle is invalid.
2008-01-17 13:56:15 Operation completed.)


what is the required steps.

Hae you tried creating the trust and what kind of was made? Have you also tried to configure DNS on both forests for the trust? Have you used xyz.local and abc.com as forest names properly or did you use asg.local somewhere else?

I found that it could be a problem if you are not using the Source Domain's PDC-E where the TCPIPClientSupport Registry key is enabled, so to do that, follow the below steps:

1. First of all try to add the following registry key to the Source Domain Controller that ADMT is pointed to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA
2. DWORD: TCIPClientSupport = 1
3. After that restart the Domain Controller.
4. Now you have to try to migrate computers to test.