How to install Windows without the original factory CD

How does a person install Windows on a computer if the customer lost the original CD? Another way to put it is you need to do a clean install of Windows and the client looses the original Windows restore disk. It happens all the time to me. You have a key but you don’t have the media!

Well, my days of tracking the software down may be over. It looks like OEM versus Retail keys are not locked to their specific versions with Windows 7. (possibly with Vista also) Unfortunately, I have found no info that says an easy way to do this with Windows XP.

Here is a link on how to go about doing it: