Whenever you install a copy of Windows 7 on your desktop it must be activated. The activation process sends your product key that you have entered while installing to be checked against the records in Microsoft Servers. This is to ensure that the same product key is not used again. Whenever you make changes to your machine configuration the activation process in the OS makes sure that the changes are reasonable and you are running the copy of the OS on the same machine.
Recently I changed the motherboard of my desktop. This is considered to be a major change almost like installing your copy of Windows 7 on a different machine. Hence I was asked to Activate my copy of Windows 7 again. Of course the activation failed and I was asked to 1) Buy a new copy of the OS, 2) Enter the product Key Again or 3) Activate by calling Microsoft Activation number.
When you decide to activate by phone the Activation Application in Windows 7 comes up with a computed Installation ID for your system. This is a set of 9 six digit numbers that are presented to you as below.
These are India based BSNL toll free numbers that you can call. I called the 1 800 11 1100 number and was greeted by the Automated Voice Response. You choose the correct menu option of activation and are asked to enter these 9 set of numbers of the installation ID. After that your call is transferred to an operator, in my case from the Bangalore call centre. You have to explain the reasons why you are trying to activate. I explained my story of having to change the motherboard. He asked me to readout three sets of the installation ID just to verify my call. Then he read out another 8 sets of 6 digit alphanumeric confirmation ID that I entered as he called it out. Then one click on the NEXT Button and my copy of Windows 7 was activated.