Logon to Windows 2003 AD using a windows 7 client.

Hello

I have posted the following question 3 days ago and got two suggestions. Actually, both solutions suggested almost the same action. However, the suggested solutions didn't work out for me. My original question was as follows:
-------------------------
"We have a server running on Windows Server 2003 to manage 60 PC's in our school laboratory. This week we upgraded the operating system of 10 PC's from Windows XP Pro to Windows 7 Enterprise. Afterward,  10 PC's were joined to the existing Windows Server 2003 domain. Users are defined on AD and there is no problem with PC's  running Windows XP Pro. Unfortunately  when we tried to log on to Windows 2003 domain using Windows 7 we got the following error message;

"The security database on the server does not have a computer account for this workstation trust relationship"

So we ended up with no luck but we need the solution as soon as possible.

I hope some  of you have encountered this problem before and could kindly suggest a solution. Thank for your concern and help in advance."
--------------------------
I followed the suggested the solutions as I explained below:

I removed the windows 7 computer from the domain and joined the domain again. When I tried to remove the  win7 computer from the domain I got the following error message;

"Changing the primary Domain DNS name of this computer to " " failed. The error message was : The remote call failed and did not execute"

I ignored this message and removed the win7 computer from the domain and joined the domain. But I can't still logon to windows 2003 AD. When I tried to logon I got the following message :(

"The security database on the server doesn't have a computer account for  this workstation trust relationship".

Would you please let me know If I missed something ? Thank you.