Is your CD reader installed ? If so, just run OS 3.9 installer from the OS 3.9 CD and choose an option that is more or less called "Create an Emergency-disk".
If your CD reader is not installed, you can install the demo-version of IDEfix from Aminet in order to detect it. Or I can send an Emergency-disk to you. But if you are not browsing on your Amiga, in any case you'd have to transfer a file from another computer.
