This thread should show you the way. It has 3 Dos and 5 Windows inside plus "a few" Linux.
It is dead simple. So don't laugh!
You install 1st MS system. Get it working. Then Use Grub floppy (or Grub pen drive or Grub CD) to hide it. The MS system should nuke whatever in the MBR.
You then install the 2nd MS system. It can't see the 1st one so it will be installed in a C drive. After getting it in a working order you hide it again. The 2nd MS system hoses the 1st system's MBR.
You do the same with the 3rd system.
You do the same with the 4rd system.
You do the same with the 5rd system.
You do the same with the 7rd system.
You do the same with the 3rd system.
You then restore Grub in the MBR and edit the menu.lst to
Unhide the partition you want to boot, make it active and hide all the MS partitions that are in front of the MS system you are booting (otherwise it will rob its "c" drive status).
This method allows you to keep a boot loader for each system. Therefore it is a lot easier to maintain and rescue each one. There is no limit to the MS systems you can handle.
Just remember to install a MS system as a stand alone system it needs a primary partition to reside in and there are only 4 primaries in any hard disk. The other way is to go virtual machine.
By the way when a partition is hidden it merely toggles a binary bit in its partition type. Thus a ntfs partition type 7 is hidden when it is 17. A fat32 partition is type c and hidding it is to make it type 1c. MS systems do not support partition type other than its own kind so PC users have been using this known behaviour to multi-boot MS systems. If you must know more here is
a thread I tried to explain it more. Hidden partitions support is inside every Linux. You can see them listed in fdisk, cfdisk and sfdisk. The wheel has been invented many years ago. I just use it.