I'm also having problems joining a domain with Windows 7 RTM...
I previously used an XP computer on the domain wth a name like 'mylaptop'.
I replaced the drive and have Windows 7 Ultimate installed and am unable to join the computer 'mylaptop' to the domain. I've done these things...
1. Ran NSLOOKUP to verify I can see the domain controller
2. Manually entered the DC IP number in DNS
3. Disable IPv6
4. Enabled netbios over TCP
5. Can successfully ping both DCs
6. Disabled all firewalls
7. Tweaked secpol.msc settings as described in other posts
8. Asked the domain administrator to manually remove the mylaptop account from the domain.
I'm not an admin, but I was given rights to join a computer to the domain. I can successfully use remoted desktop to get to other computers. I can browse the network and manually enter credentials to see shares. Networking seems to be OK.
When I attempt to join, I get the message:
Your computer could not be joined to the domain because the following error has occurred: No mapping between account names and security IDs was done.
or this error:
The join operation was not successful. The could be because an existing computer account having the name xxxx was previously created using a different set of credentials. Access is denied.
I verified that the account was in fact deleted.
I tried using Powershell's add-computer (run as admin) cmdlet with no success (apparently there are bugs).
I tried all of the suggestions below with no success...
Before I go any further, this posting is a solution (or an article to give ideas) for those people that are having problems with Vista in a corporate or advanced home networking environment. Sometimes, I am so upset by the problems I encounter when using computers that I have to do my bit for world peace and share some knowledge in the vain hope that others may be spared the frustration.
Problem: When adding a computer running Windows Vista to a domain, you receive the following error:
In fact, there's a lot more to the error message than this, but it ends with those two words. I've tried to recall the rest of the long message but the jist of it is that its saying it could be caused by an existing computer account on the domain and to rename the machine or remove the account - which is all lies.
Solution: Unsecure your Vista PC, because afterall, there's no way of pinpointing which of the millions of restrictions are preventing you from getting on with your life.
I admit that I have muddied the waters somewhat as another error I was receiving told me that the SRV record for my DC was not available in DNS*, but essentially I did the following:
Ensured that the problem was due to local rights by entering an intentionally incorrect domain administrator username and password - this gave a different error message
Opened MMC (mmc.exe) and added the Local Computer Policy snap-in (File menu).
Navigated to Computer Configuration\Windows Settings\Security Settings\Local Policies
Opened User Rights Assignments
Added the Administrators group to the right: Add workstations to domain
Opened Security Options
Disabled the option: Domain member: Digitally encrypt or sign secure channel data (always)
Disabled the option: Domain member: Disable machine account password changes
Disabled the option: User Account Control: Admin approval mode for the Built-in Administrator account
Set "Elevate without prompting" on: User Account Control: Behaviour of the elevation prompt for administrators in Admin Approval Mode
Disabled the option: User Account Control: Run all administrators in Admin Approval Mode
Opened Windows Firewall with Advanced Security
Switched off Windows Firewall for all three profiles
Ensured that my time settings and timezone were the same as the server's
Upgraded my newly installed Windows 2000 domain controller to SP3
Note that once you've joined the domain, the local policy will become obsolete anyway.
Now Reboot. Although apparently happening live (Vista doesn't hesitate in putting up a red shield in the system tray as soon as you tweak the settings), the solution needs a restart. I only did this after reading that with UAC switched on, your administrative account actually runs Explorer with two security tokens, and most activities are performed using the plebian user token (so you're never really an admin) - this led me to think that the add to domain wizard was actually running in pleb mode. The restart worked and I was able to get myself on my domain. The end.
I must admit that it is a shame that Windows cannot tell you what settings are effecting a security block. The solution becomes one of all or nothing; my new-build apartment has a legally required smoke-detector just above the door to the kitchen - you know, that place where you make heat and smoke - consequently I've had to crippled it with a rubber item usually associated with birth control. So I am unprotected from fire in the living room and I am unprotected by Microsoft's
new security features.