Uninstalling XP Home, Install 98 SE

You cannot install an older version of Windows over the top of a newer version.

The ONLY good way to replace Windows XP with Windows 98 is to FORMAT the hard drive, and start over from scratch.

Start by downloading and running Belarc Advisor
www.belarc.com
(more on this later)
Print out the report.

Make sure that you back up any critical files and settings information first.

Create, or download a W98 startup disk (www.bootdisk.com)

Set the PC to boot from floppy.

Run fdisk at the DOS prompt
(www.fdisk.com/fdisk for links to tutorials)
Verify that you have a Primary DOS partition.
If fdisk reports a non-DOS partition, you will need to delete the partition before proceeding.

If needed, re-boot the PC and run fdisk again to create at least a Primary DOS partition, and make it active.

There is a good article on partition strategy posted at www.aumha.org

Re-boot, and format the C: drive
format C: /s

After the format is complete, run setup with the W98 CD in the drive.

After Windows 98 is installed, you will need to find and download drivers for the hardware.
Look at the Belarc report.
You will need to download and install in order:

Chip-set drivers for the motherboard.
Download these from Intel, AMD, VIA, SiS, or whomever.

DirectX From Microsoft

Video driver:
Again from the chip mfg.

Sound driver

Modem driver

Monitor driver

any other hardware device driver.

Chas

Why would you want to degrade your OS to 98?
Is there any specific cause for this?
Maybe you would like to voice and see if Chas can help you with that. And 98 may not have the necessary drivers for your devices. (You can try to search though)

Otherwise, it would be like what Chas said, you will have to clean install 98.