What happens if you do an fdisk /mbr from a Win95 boot disk?

VivienM wrote on 2025-02-05, 02:47:

What happens if you do an fdisk /mbr from a Win95 boot disk?

+1

Doing a SYS C: may also help.

Edit: There's something that comes to mind, not sure if it's the issue though.
MS-DOS 7.1 and Windows 95 do handle HDDs slightly different.
In short, MS-DOS uses the BIOS to get information about the HDD whereas Windows 9x loads its own HDD drivers.

And that's were the differences may start after boot up.
The Windows drivers may "see through" and see a HDD that has different characteristics than what the BIOS says.
Especially the whole drive geometry thing, with CHS/ECHS and different LBA algorithms.

Hm. On other hand, the PC does hang straight away on "Starting MS-DOS".
So Windows 95 isn't being loaded yet and it's still all about DOS..

Edit: How old is that PC, if I may ask? A 486 or a Pentium?
If it's an old model, it might have used E-CHS aka Large rather than LBA when the 8GB was used for Windows 95 installation.
So there might be some sort of confusion about drive geometry.
Not a big one, but maybe one that can cause the partition to start at slightly different position.

Edit: Sorry if I'm talking too much right now, but I just made some coffee. 😅
Anyway, what also comes to mind is using Win32 Disk Imager and making a dump/backup of the CF card.

Then you can fire up PCem/86Box and experiment with various PC configurations and BIOSes (preferably the same type as real PC).

Or you can mess around with various tools on real PC and write back the CF card backup if needed.

Edit: Some last tip, there are a patched BIOSes at Wim's BIOS site.
They often have improved HDD support.

http://wims.rainbow-software.org/
https://www.wimsbios.com/large-hdd-patched-bios.jsp

Just keep in mind that BIOS patching can go wrong, too.
It's recommended to make a backup first. The updater program often has the backup feature, too.
Using an EPROM programmer such as TL866 is safest way, I think.

FDISK /MBR did nothing. It still just sticks post POST beep with the blinking cursor.

SYS C: gave "Cannot specify default drive."

The only thing I can think of will be to FDISK the new CF card from the Win95 boot floppy then manually copy all the files from the old CF card over to it. Ugh.

Specs:

Pentium II 450
128 MB DDR RAM
ATI Rage 128
Intel SE440BX-2 chipset, P03 BIOS revision.

I know, some smartarse is going to say "y u no run Win98" but I prefer Win95. Okay?

How about trying to do the expansion in Win11? Use HDDRawCopy tool to copy your original CF card to an IMG/IMGC file. Then bring the new larger CF card and copy the IMG/IMGC file back on it using the same program. Once done, the new card should be identical to the old one, and even retain the same 4GB size. Now go to Win11's Disk Management and expand the partition to 8GB... hopefully this could work.. You can also validate if the pre-expansion copy succeeded by directly taking the 8GB card and putting it in the DOS machine to see if it boots correctly. If it doesn't, I'd say something funky is going with your 8GB card or DOS PC BIOS.

Problem is solved. I wiped new CF card, fdisk'd to its maximum capacity of 16GB, formatted it, then copied contents of existing card over and hit it with sys C: from a floppy disk.