Save it as a file to your hard drive. Then double click on that file with a blank floppy in the drive and it will create the boot disk. If it was Windows 98SE, use the boot disk for that. Win98SE OEM is the exact listing there.
If you just changed the monitor and that was all, then I doubt that a format will solve the problem. There may be hardware issues, display settings, etc. that need to be addressed. Alas, we have no clue as to the hardware.