So I'm trying to get Windows 95 thrown on an old Pentium machine to rekindle my childhood memories but I'm having issues getting a decent sized hard drive working on the system.

I have a quite old Western Digital Caviar working fine on the system but unfortunately its only 430MB and just doesn't cut it.
I found some old IDE hard drives lying around so I've tried those - they are a Maxtor 20.4GB drive manufactured in 2000, and a Hitachi Deskstar 80GB manufactured in 2003 (which I currently have the jumpers set to master and 32GB Clip - which I believe sets the the drive to use no more than 32GB for compatibility with older BIOS')

I'm having various issues using both these drives. The Maxtor one I can create a partition on with FDISK and then format without issue but start getting problems when copying data to it.
I wasn't sure if this drive was working when I stored it away years ago so tried the Deskstar, which I know was.

I can't even get FDISK to successfully create a partition on this.
It gets stuck on 'Verifying Drive Integrity' for a while where it goes up to 5% and then resets to 0% and starts again.
After a while it says not enough space to create DOS partition or something.
If I try to format it, it says its only 124.98MB in size and fails to format anyway.
It will say 'Trying to recover allocation unit' for a while and then fails with 'Error writing FAT. Format terminated.'

I should state at this point that I put both these drives in a USB enclosure and formatted them in Windows 10 disk management as FAT32 first to test they worked, and both seemed fine - I was able to copy and pull data off the drives in Windows 10. I'm getting a contradiction here - the WD Caviar working perfectly suggests the mobo and cables are all good. But the newer drives working in Windows 10 but not in this machine would suggest to me that something is faulty on the old machine.

My question here is not 'Please can someone tell me if my HD's are faulty' but rather does anyone know if I might be having compatibility issues with slightly newer drives and older hardware, or could this be a motherboard issue?

If it is a mobo issue, this could be very problematic as it looks somewhat proprietary and I don't know if it would be possible to find another that fits the slots in the back of the case properly.

I appreciate that you'll probably want to know the motherboard make/model - at this point I can't give that information as I'm about to head off to work for a 12 hour night shift, but I will post this information tomorrow.
The computer is a Fujitsu ICL Indiana desktop which I imagine dates from around 1996.