If you can set your BIOS to boot from the CDROM, an original Win98SE CD (or image copy of one) is bootable.
If not, boot from a Win98SE floppy, manually FDISK and FORMAT the hard drive so the partitions are the way you want them, and install a bootable DOS 7 layout in the primary boot partition with a working CDROM driver:
config.sys
device=c:\dos\himem.sys
dos=high,umb
device=c:\dos\emm386.exe noems
devicehigh=c:\dos\oakcdrom.sys /d:mscd001
autoexec.bat
@echo off
lh c:\dos\mscdex.exe /d:mscd001 /m:12
Copy the OAKCDROM.SYS, EMM386.EXE, and HIMEM.SYS from the floppy, and MSCDEX.EXE from the RAM drive the floppy puts up, to the temporary DOS directory on the hard drive. (If you can't find EMM386.EXE, leave off the third line in CONFIG.SYS, the 'high' in 'devicehigh' in the fourth, and the 'lh' in the second AUTOEXEC.BAT line.)
Reboot to the hard drive with the CDROM drive installed, and you should be able to select the CDROM and run SETUP.EXE in the root directory.
If the backslash key is shot, try holding the ALT key down and typing 092 or 0092 on the number pad (you may need to use NumLock or Fn to access the 'embedded numpad' feature for this).