PS! This tutorial is for VirtualBox, but the same steps should be possible with real hardware (roughly).
While it’s virtually possible to increase disk size of an existing disk with Virtual Media Manager, you’ll need special software in DOS to create the new partition and merge partition with the existing one.
In this example we will completely replace the old harddrive with a new bigger one.
With Virtualbox, a new harddrive is cheap.
Step 1 – Create a new drive
In Virtualbox, go to Virtual Media Manager (CRTL+D)
Click Create:
We will go with a VDI drive, hit next:
We suggest to use Dynamically allocated to avoid taking up all disk space before we need it. Hit next:
Write the name you want for the new virtual drive. We call it biggerdrive.vdi.
Choose size of disk. Note! 2GB is maximum in MS-DOS.
Hit Create:
Step 2 – Assign the new drive to your VM
The original C drive is IDE Primary Master, we need to add a Secondary Master.
Click add harddisk:
Choose your new biggerdrive.vdi. Hit Choose:
Step 3 – Make new drive ready in MS-DOS
Start your VM. Your new drive (Secondary Master) will be assigned as the D:\ drive.
However, to be able to use it you need to partition and format the drive.
From the C:\ prompt, write fdisk and hit enter.
First we need to choose the new drive, hit 5 “Change current fixed disk drive”
Now, choose 2, which is the new 2GB drive.
Now we want to create the partition, make sure choice is 1 and hit enter:
We want to create a primary DOS partition. Hit Enter:
In this example we want the whole drive as one partition, hit enter:
After this process, hit Escape out of fdisk and machine will reboot.
Now we need to format the partition, from c:\ prompt write “format d:” (without the quotes).
You will get a warning that all data will be lost. We know this disk is empty so we write Y for yes to proceed. In Volume label you can call the drive a name by choice. Do so and hit enter.
Step 4 – Copy all content of C drive to your new drive
From your D:\ prompt write “xcopy c:\*.* /a /e
This will copy everything from C drive into D drive
Step 5 – Switch out the old drive with the new one
Now we want the new drive to be c:\ and we don’t need the old drive anymore.
In Virtualbox under the storage section, RMB on the original drive and remove attachment:
Set the new drive to “IDE Primary Master”
Now we will NOT be able to boot the machine as there is no master boot record on our new drive.
We need to boot the machine from a boot diskette. A diskette image (.img ) can be downloaded from https://www.allbootdisks.com/
Insert the image into the Floppy section in Storage, and make sure your Boot order is set to start from Floppy:
Now boot your VM from the floppy.
Now we need to make the new harddrive bootable so we need to set partition as active.
Again we head into fdisk. From a:\ prompt.
Now choose the option 2 – Set active partition
We only have one partition so hit 1 and enter:
Hit Escape out of fdisk and your VM will reboot, again from the floppy diskette.
Now we want to write the master boot record (mbr) to the new harddrive.
From a:\ prompt write “sys c:”
The system will say “System transferred”.
Now you can power off the machine, remove the floppy and start your VM from your new “big” 2GB drive!
