If you have a volume license (also known as corporate ed.) the system will simply check the license/product key that is associated with the system and see if it is valid. The verification is different for these systems because Volume License/Corp Ed.'s do not require online validation at the time of installation, or after hardware upgrade/swaps.
MS explains validation:
Validation is a short process that enables you to verify that your copy of Windows is genuine. If you request a download of genuine Microsoft software from the Microsoft Download Center, you will be prompted to complete the validation process. You may choose not to validate your software and still obtain your requested download. However, validating now will enable faster access to the Download Center in the future when validation may be required. Following the validation process, you’ll be taken back to the initial download details page to obtain your requested download.
At this time Validation is completely optional, but in the future, this could be required to access Windows Updates. You can read about it in more detail here. And if you want to try the Validator out yourself, then you can find it here.