I've seen this problem a lot (it's quite common). I'm going to give you a step by step procedure. If you need any or all of the files that I mention, email or PM me and I'll email them to you. NOTE: You will need to be able to boot from CD-ROM in order to use this method.

1. Format a floppy drive as a bootable system disk.
2. Copy FORMAT.COM and FDISK.EXE to the floppy disk.
3. Boot from the floppy drive.
4. Run FDISK.EXE and delete ALL partitions on the hard drive.
5. Create a PRIMARY DOS PARTITION in FDISK.
6. Exit FDISK and reboot from the floppy.
7. Format the new partition using FORMAT.COM (type "format [drive]:").
8. Put the CD for whichever version of Windows you want into your bootable CD drive and remove the floppy disk.
9. Reboot from the CD and install Windows.

*NOTE: You will need the WINDOWS 98 VERSION of FDISK.

Hope this helps.