Are you looking to install DOS 6.22 to a FAT partition after the fact of having W2K already installed, or are you planning on installing DOS first and then performing a clean install of W2K? If you plan on performing the latter, it's a much easier process since you won't have to worry about DOS 6.22 overwriting the W2K boot sector after running the
sys c: command.
You could also format the primary partition using FAT or FAT32 (meaning using a program like Partition Magic to convert from NTFS), and perform the following...
1. Boot your machine with a Win98/Me boot disk.
2. Run the command
sys c:
3. Get a copy of BootPart.exe from...
http://ourworld.compuserve.com/homepages/gvollant/bootpart.htm
4. Use Bootpart.exe to restore your W2K boot sector (BootPart.exe only mentions NT boot sectors, but it works on W2K also).
5. Use BootPart.exe to create a DOS boot sector file.
6. Use BootPart.exe to modify the Boot.ini for a dual boot.
Better yet would be to format a partition no larger than 2GB in FAT for DOS 6.22, install DOS to that partition, then install W2K to the second partition formatted using NTFS. W2K will see the DOS OS during Setup, and modify the Boot.ini accordingly so as you'll have the choice of booting to either DOS or W2K at the boot menu screen.