If you have FAT32, then it is not possible to boot back into any of the "old" DOSs, ie 6.22...
If you want to install Win98/WinME, you must have your primary active partition as FAT32, because Win98/ME needs it boot files to reside there, regardless of what partition you actually install Win98/ME to.
So if you have Win2K on C: with NTFS, you need to convert C: into FAT32.
To install Win98/ME, I think you will need a Win98 boot disk. Boot to a DOS prompt from that and install from there. After that you will need to do a repair for Win2K/NT for the boot loader.
Messy, but can be done.