1. First you'll need a bootable floppy disk. You can set one up from within Windows or download an image from
Bootdisk.com.
2. Boot using the floppy drive. When you get to the A: prompt, type FDISK.
3. Using FDISK, you'll see the partition for your C: drive that contains your current windows install. Delete this partition, then create a new one in its place. Exit FDISK and reboot using the floppy disk. Be sure to choose the option "With CD-ROM support" when you reboot.
4. Type FDISK /MBR to make sure that no viruses are in the master boot record of your hard drive.
5. Format your fresh C: partition by typing FORMAT C: from the A: drive.
6. Once your format is complete, insert your Windows 98 CD. Type D: (or whatever drive letter your CD-ROM drive was assigned), then type SETUP. You should have a clean install of Windows now.
7. Before you connect your computer to the internet, be sure to
download and install any Windows 98 updates. Download them on another computer, burn them to a CD, then install them on your Windows 98 box.
Good luck, let us know if you have any more questions.