Okay this 'should' work, heres a guide first but I'll run through the basics. Please note though i'm doing this from memory so i suggest doing a google search and reading other guides.
http://www.informationweek.com/story/showArticle.jhtml?articleID=14700253#_boot to Windows as usual.
Drop a blank floppy in your drive.
Go to my computer, select A drive then right click and select format.
A box should come up, then put a tick in the box that says create an ms dos start up disk. A copy of ms dos will now be created.
reboot your PC and go into the bios(the key to press will be on the bootup screen), change the boot priority to floppy first then exit saving changes.
make sure the floppy is in the drive for start up and ms-dos will now start to boot.
select option 1 from the list "boot with cd rom support"
once booted ms-dos will be there 'a:\'
type 'format c:' BE AWARE this will wipe your hardrive.
when its finished type 'd:\' and make sure your windows 98 cd is in the drive.
type setup.exe to begin to install windows 98
Like I said please make sure you check the guide, but there is no reason to replace your hardware as all you need to do is format the harddrive.