I believe I only had a Windows 98 'Upgrade' CD, which could not be used to install on a bare system. This meant I had to first install a previous copy Windows, which in my case was Windows 95 on floppy disks (and I feel like it was 20 disks, at least for my installation).
This worked fine until one re-install disk 15 decided to fail on me. I managed to hack it back together by copying the files that were still accessible to a different computer and then copying them to a blank floppy together with the missing files from the running system's Windows folder (I think it was a couple of dlls that were unreadable). I was surprised that it worked.