How do I reinstall Microsoft Office 2003 without the original install disk?

I have Microsoft Office 2003 Professional installed on a computer, legally licensed, activated and registered. However, I have lost the install disk and want to install the program to a computer I have purchased to replace the system the software is installed on.

I called Microsoft to get replacement disks, however, they told me they quit supporting this 5 months ago, and told me my only option is to purchase the software again. There has to be a different way to reinstall my legally licensed program without paying for the program again.