Windows 7 - Help with Repair Install

I want to do a Repair Install on a machine with Windows 7 Professional pre-installed and without any disk. However, I do have another copy of Windows 7 Professional. The Repair Install tutorial mentions entering the serial number of the disk in the course of the process. It also mentions that the version must be the same or higher. What is not clear is what happens if I use the Windows 7 disk as the serial number will not match the one for Windows 7 as installed.

There is no serial connected with the Windows 7 install DVD - it is only an installer, and can be used for retail or factory OEM.

So you can indeed use the same version retail installer to Repair Install your factory OEM pre-installed Windows 7, just be sure after install to activate at Computer>Properties using the Product Key on COA sticker on machine.

Follow these steps and choose to remain connected to the internet to get the latest Updates and drivers into installer which is over a year old now: Repair Install

Thank you