Joining your vista PC to your domain is same as XP machine check the one of the following solution.
Start—>Control Panel and Select System and Maintenance.
Click the System section.In the “Computer name, domain, and workgroup settings” section, click the “Change settings” link.
If you’re prompted by the User Account Control module to continue, click Continue.
In the Computer Name tab of the properties, click the Change button.
In the “Member of” section, select Domain and enter the name of the domain and click OK.
You’ll be prompted for an account with rights to join the computer to the domain. Enter the details and click OK.
Click OK to the welcome dialog box.Click OK to the notice that the machine will be rebooted.
Click Close to the dialog box.
Click Restart Now to the restart prompt.
Once the reboot is complete, the machine will be part of your domain.
Use Netdom.exe to add the computer to the domain.
netdom join ComputerName /domain:DomainName /userd:UserName /passwordd:UserPassword
Yes, there is a letter “d” after user and password in the netdom command.
Download netdom from here
On your XP installation disk, you must run the setup.exe under Support/Tools. Afterwards, you will find it under c:\program files\Support Tools\Netdom.exe