Really, I have not done this myself.
Here is plan I am going to try just to see if it works. Using a plain 40 GB ATA drive, partition it it thus:
200 GB fat32 | 500 GB FAT16 | 38 GB NTFS| Rest unallocated
Use a partition maker like GPART or early version of EASUS.
Prepare a floppy drive with a fdisk program.
Set first partition active. Install a basic boot loader. Test it
Use floppy to set second partition active.
Install DOS 6.22 thee on the second partition.
Use disk again to swap active partition to see if it works.
Next eat third partition active. Install Windows 7 there.
Next install a partition manager that can switch the partitions. The first partition is a 'sacrificial lamb' used to satisfy Windows 7 appetite for messing the first partition.
I am still doing research on this. I am not sure if System Commander can do this.
Here are two references that are 'in the rough', but are a starting place.
http://en.wikipedia.org/wiki/Multi_boothttp://en.wikipedia.org/wiki/Ranish_Partition_ManagerEDIT:
Possible solution.
http://www.plop.at/en/bootmanager.html