AFAIK you can't for HDDs and native FDDs, they are always auto assigned according to "modern" (DOS 4+) rules - while CDs and other removable drives (ie hotswappable drives expected to always have a single partition, though I suspect the difference is in having native Int13 support) are assigned in the device manager (and can steal drive letters from the above logic, but the order of the non-reassignable drives is fixed; in the same way, a partition manager can't rearrange drive letters, just influence the order by hiding them or converting between primary and logical) 😀

Of course someone has probably made a 3rd party driver to change that, but if it exists I've never looked for it!

Imagine if Win9x let you do this. Every time you used a boot disk, or used the F8 boot menu to boot command prompt only, or did "restart in MS-DOS mode" the drive letters would resort back to the default DOS rules that Ryccardo mentioned above. Since exiting to DOS was a necessary feature of these OSes you wouldn't want that inconsistency.

That's why I'm all for hardware solutions, like switching master/slave via cable select line and a switch.
That way, the operating system on the currently bootable (master) HDD always is C: no matter what.

This guy has a tutorial how to make such a cable: http://www.stefanv.com/electronics/ide_dual_boot.html

psaez wrote on 2024-07-03, 16:03:

How can a partition letter be changed in 95 and 98 without using a partition manager?

It is sort of possible with certain utilities such Drive Letter Manipulator and Letter Assigner.

DLManip works exactly for this.

Use DLManip in autoexec.bat and use the MOVE command to move D: to G: example DLMANIP.com MOVE D: G:

MS-DOS 6.x used to have a similar feature built-in for supporting its own Double Space.
It's an undocumented feature, though, not meant for other software.

Why do you want to?
I hate how newer OS's keep moving my c:\ drive.

My typical setup is something like:
c:\ win98 (fat32, visible to all OS's)
d:\ data (fat32, visible to all OS's)
e:\ WinXP (NTFS, only visible to XP)

That means though that no matter which OS I'm in I know exactly where everything is instead of "did I save that in Win7 or Win10 c:\"

chinny22 wrote on 2024-07-04, 04:45:

Why do you want to? I hate how newer OS's keep moving my c:\ drive. […]
Show full quote

Why do you want to?
I hate how newer OS's keep moving my c:\ drive.

My typical setup is something like:
c:\ win98 (fat32, visible to all OS's)
d:\ data (fat32, visible to all OS's)
e:\ WinXP (NTFS, only visible to XP)

That means though that no matter which OS I'm in I know exactly where everything is instead of "did I save that in Win7 or Win10 c:\"

having WinXP installed in E is not a problem for you? I got all messed up when I did that... everything tryes to install in C:\ where W98 is, and even some temp files and some software data goes to the W98 partition. Are you sure you don't have problems with Windows XP being in E and the OS knowing that C exists?

I tried it recently and had no trouble with it. WinXP keeps its Program Files and user data on its drive. The only thing it will change on C in such case is that it will install its bootloader there, which will show the boot menu for XP vs. Win98.

You'll need to be careful when installing software to not accidentally put them on C, but by default the installer is smart enough to not hard-code to C:\Program Files and instead query the OS for the location.

This is how I've done it since 1999, starting with 9x/NT4 and never had a problem.
as wbahnassi said, some programs will still default to C:\ but allow you to change the install drive with no side effects.

Not saying some software isn't hard coded to c:\ but in my experience its only badly written small time business software which I doubt anyone installs on a retro gaming PC.