I installed Windows 7 in my office PC and it's working fine. After adding the machine to Domain, I'm unable to change the themes, windows color settings etc. as it's disabled. how to restore this feature?

Sounds like group policy.

Open the Local Group Policy Editor. If you don't know how to do that, look here. Next, look under "User Configuration > Administrative Templates > Control Panel". Check that "Hide specific Control Panel items" and "Show only specified Control Panel items" are set to disabled.If they are, change into the subfolder "Personalisation". Here, check that "Prevent changing colour scheme", "Prevent changing theme", "Prevent changing visual style for windows and buttons" and "Prevent changing window colour and appearance" are disabled. If they're not, you can't change themes etc. Also, at the end of the list, check that "Force a specific visual style" is also disabled. Also this, if enabled, disables changing themes etc.

Hi, It is also recommended to contact domain administrator to check if there is a related group policy in domain. Thanks.

The domain policy will overide the local policy so you have to check the domain policy in "Users and Computers" for your domain. So even if you edit the local it will do no good.

Logon using an administrative domainaccount or the local admin account of your machine. <machine name>\username to see if those options come back, if they do then a domain policy is being applied to either your machine or user account after logging in as a user other than an administrator. You can also run "gpresult" to see what policies are being applied when your logged on provided you have the right to use the command prompt. You may have to right-click the command prompt and "run as administrator" before running "gpresult" or......Start>Run>cmd (CTRL+SHIFT+ENTER) to run as administrator