I don't know which way is better. I’ll tell you which one I originally used (In the future, nothing fundamentally changed, only new disks were added, the entire “configuration” was upgraded from IDE PATA HDD to a new AHCI SATA SSD (With Rudolph AHCI DRIVER). The size and purpose of partitions and new, added later, physical disks). In general, conceptually, everything is the same.

All this is by no means advice, you can consider it "how not to do it." However, this configuration has stood the test of time (more than 10 years).

I personally do not see the slightest sense in all these unnecessary troubles to hide the OS from each other (It will be more difficult, for example, to repair / modify / backup one OS from another), as well as the troubles with "Each OS on its own C:", since Windows XP lives fine on D: without any problems. It is extremely rare to find software that would forcibly (without asking the user) install something on C:. This is a rare antediluvian software, which, if for some reason it is needed, in a good way, it would be worthwhile to first repackage it into an acceptable form on a virtual machine. Although you can use it "as is" (By then deleting these temporary files, which it will leave in a temporary folder on C: or D:). This "problem" is exaggerated. I also do not see any problems in using FDISK and, as a result, using XP on the logical drive. Also, there is not the slightest need to use XP on an NTFS partition (On the contrary, this creates new difficulties for the user, for example, with rights, as well as hidden folders in the root and normal access from Windows 98), because it can be installed out of the box on FAT32 and this should be appreciated, because later OSes can no longer do this and NTFS is generally really needed only for files larger than 4GB (A separate partition is used for this, see below).

I made it easy for myself. Prepared the FDISK disk. The first partition is FAT16 on 2GB (For MS-DOS 6.22 and Windows 98 multiboot), the second is extended, in which the first logical drive for Windows XP is 8GB in FAT32, the second logical drive for programs and games is 128GB FAT32 (These programs and games are common and can be used from any OS), as well as all the remaining space for a separate large 262GB NTFS partition (For backups of partitions with OS, ISO images of games, installers, files, etc. That is, this is a storage partition). This partition can also be accessed from Windows 98 using Paragon UNTFS for Windows 98 and the patched ESDI_506.PDR (For Large Disk Support).

MS-DOS 6.22 was installed first, then Windows 98 and Windows XP.

Everything was carried out only by built-in standard tools (FDISK, Windows XP Disk Management). You can format partitions larger than 32GB to FAT32 from Windows 98 using standard tools. Multiboots, with this installation sequence, are created automatically. If you are doing this for the first time, you can practice in a virtual machine.

But to create a backup, it is better to use something independent, such as CloneZilla (Creates an exact sector-by-sector copy of the entire disk or partition), which is loaded from CD\USB. With this option, all bootloaders, all OSes will be on the same partition of disk C: (2GB, FAT16) and in order to restore the boot of all OSes at once (MS-DOS, Win98, XP, Win7) in case of transfer or replacement of the disk, it will be enough to restore from backup only the C: drive, and the rest of the OS will only need to be copied to their respective partitions.

By the way, in new operating systems like Windows 10, Microsoft eventually came up with this option (The first small hidden partition with a bootloader). Here it turns out a little more, but with two full-fledged OS (98 + DOS).

DoZator wrote on 2022-12-26, 14:55:

It is extremely rare to find software that would forcibly (without asking the user) install something on C:.

Sometimes you don't even notice, because a lot of installers are simply broken so you get parts on the C: drive that you do not want there.
There are also games that think the D: drive always must be the CD-ROM drive, so they break if Windows is installed on that drive.

While rare, things can go wrong if Windows is not installed on C:, so I avoid that every time.

I also don't like newer versions of Windows hijacking the bootloader of the old one. Windows 10/11 are the worst for this, because they need a full reboot to boot into the older operating system, which is just very tedious.

schmatzler wrote on 2022-12-26, 16:10:

Sometimes you don't even notice, because a lot of installers are simply broken so you get parts on the C: drive that you do not […]
Show full quote

DoZator wrote on 2022-12-26, 14:55:

It is extremely rare to find software that would forcibly (without asking the user) install something on C:.

Sometimes you don't even notice, because a lot of installers are simply broken so you get parts on the C: drive that you do not want there.
There are also games that think the D: drive always must be the CD-ROM drive, so they break if Windows is installed on that drive.
While rare, things can go wrong if Windows is not installed on C:, so I avoid that every time.

It is this kind of things where there are probably more folks talking about it on VOGONS, than pieces of such software in existence. So, yes, "extremely rare" is probably correct. Take it from a guy who has had hard drive split into at least 4 partitions since his first MS-DOS machine, and Win98 installed on G: from day 1 (the boot files are on C: obviously).

schmatzler wrote on 2022-12-26, 16:10:

I also don't like newer versions of Windows hijacking the bootloader of the old one. Windows 10/11 are the worst for this, because they need a full reboot to boot into the older operating system, which is just very tedious.

Well, what other proposal you have? It is the only way to do it without third-party tools. The old OS is oblivious to the existence of the new OS, so it cannot account for it in any way. The new OS boot loader is written to add backwards compatibility to the old OS. It's been working remarkably well since the early NT days.

3rd party tools give you a lot more control and flexibility, and make it possible to create 'sterile' environments without any OS interference, that's true. However, Microsoft has been consistently doing the right thing by ensuring that they provide their customers a path to upgrade/multi-boot their Windows operating systems without requiring them to use 3rd party tools.

schmatzler wrote on 2022-12-26, 16:10:

Sometimes you don't even notice, because a lot of installers are simply broken so you get parts on the C: drive that you do not […]
Show full quote

DoZator wrote on 2022-12-26, 14:55:

It is extremely rare to find software that would forcibly (without asking the user) install something on C:.

Sometimes you don't even notice, because a lot of installers are simply broken so you get parts on the C: drive that you do not want there.
There are also games that think the D: drive always must be the CD-ROM drive, so they break if Windows is installed on that drive.

While rare, things can go wrong if Windows is not installed on C:, so I avoid that every time.

I also don't like newer versions of Windows hijacking the bootloader of the old one. Windows 10/11 are the worst for this, because they need a full reboot to boot into the older operating system, which is just very tedious.

Windows 98 is installed exactly on C:, so there is no problem here. Programs and games from the XP era are no longer generally tethered. Above - even more so.

In general, under Windows 7 you can assign any letters to the drive (Including D 😀, the default boot drive is already "C:". In XP, the default drive is already "D:". Under Windows 98 options are possible. It has such a feature (bug or feature) that when installing a new disk or even a USB flash drive, the letters of partitions or disks (Including CD) can move to the right. Also, changes in the BIOS of the system sometimes lead to this effect. There is even a separate unofficial patch for this feature. There is also "LetterAssigner", with which, in any such case, it is possible to set the drive (Virtual or real) to exactly the letter "D:". Whether it is possible to completely dispense with these third-party things here, I do not know. Probably somehow possible.

If you don't mind, could you remember a game for which the CD drive must be exactly in "D:". I want to test all this again and figure out what can be done with it, what options are there (Besides NoCD, RePack, LetterAssigner, unofficial patch and other third-party solutions). Find a standard way to make it work. After all, we are not going to refuse flash drives and we will probably add more disks. Although you can do without them, using, for example, an additional network drive or the main system drive of a very large size, and inserting and removing a flash drive, only as needed (performing a reboot). But these are also all workarounds, compromises, and not full-fledged solutions.

The same as if there is both a real and a virtual CD\DVD drive, because only one of them can be on "D:"

You can still try to create additional logical drives after the system is installed and running and the drive is already registered on "D:", but this does not guarantee, however, that the drive will not leave later (In view of just that bug\feature), as well as after adding a USB flash drive or disk.

I recorded a small demonstration of a regular multiboot, which is created by default, without using third-party things (MS-DOS 6.22 + Win98 + XP + 7):

Here, however, I did not pay due attention to the position of the CD drive, partitions and disks were created immediately, even before the first running Windows 98. Maybe that's what matters. Will have to try differently. It is worth noting that in XP the drive initially turned out to be "D:". And in Windows 7, just like in Windows 98 on "F:".