windows98/windows2000

Since I install Windows 2000 on my computer, I have had just problems with it. I keep the windows 98 but now my disk is formatted as NTFS and I cannot use my windows 98 anymore. How I can format my disk again and start over, with FAT32 to both? How I can create space (FAT32) to my Windows 98? I did try to repair it, but with no results. Can you help me?