Dell Windows Server 2003 Standard OEM Disk missing need to reinstall

I have a dell poweredge 800 server running windows server 2003 standard that I need to reinstall. The media disk ha been missing since I took over the companies IT department. I have a hologram windows server 2003 standard disk that I used and I used key finder to get the cd key but when I enter the key of course I get the error message "the product id volume license key is not valid"

Any suggestions on what I can do?

I have contacted Dell and since its End of Life they cannot send a disk.

Thanks