Installing IIS on windows 2003 without the windows CD
Do you have an I386 folder on the machine? If so you should be able to install it from there.
It will prompt you for SP2 files first -- these are in your Windows\ServicePackFiles\i386. Then it will prompt you for Windows Server 2003 RTM files -- these are on the CD. You can use any CD -- it does not have to be the same key as the one you've used to install with.
You also can take this from another server in your network "\server\C$" and then select the i386 folder.