Another also...
It's a long time ago but I think Windows 98 installation had to go via a floppy disk drive that booted with CD drivers. If it was an official set up floppy, the installation would proceed without further intervention but if it was just a basic boot floppy with CD support you had to issue dos commands to switch to the CD drive letter and then execute the setup.exe program.
http://support.microsoft.com/kb/221829
Maybe some later Windows 98 CDs were directly bootable but I'm not sure about this.
Tricky