If something doesn't work as expected at any point, please say so. It's important that all instructions are carried out in order.
Your BIOS boot order is set to boot from floppy isn't it? If not, enter the BIOS, find the boot order settings and set it to boot from floppy first.
<Edit> Having reread your post, this is where your problem lies. Set the boot order to A: CDROM: C:.
I thought you would have realised that the system wasn't booting from floppy. When it does, it's noisy and slow.
When it doesn't, you don't get an A:/> prompt.
Anyway, set the boot order and take it from here:
Use the floppy you created to boot the affected computer.
At the A:/> prompt, type delpart followed by enter. A small program will open. In that program, elect to delete all partitions. OK it all and reboot with the diskette still in the drive.
At the A:/> prompt, type fdisk followed by enter. Enable large disk support when asked and create your partition(s). Reboot when done.
At the A:/> prompt, type fdisk /mbr followed by enter. When that's done, type format c: /u followed by enter.
When that's complete, place the Win98 CD in the first CD drive and type v: followed by enter.
At the V:/> prompt, type setup /ie /im /is /nr followed by enter.
The Win98 setup routine will now run.
If you're not sure about something at any point, ask.