[gary]

Hi David,

You didn't happen to mention whether you are using VMware or VirtualBox.
I will assume VMWare in the discussion below.

I can tell you if you create the virtual hard disk with a capacity set to some arbitrary large value,
then after installing Windows 10, your C folder will show it has used 26GB.

As you noted you can set up VMWare so that the virtual file hard drive does not pre-allocate the
disk space but instead will simply allocate file space from the host machine to the guest
machine on demand.

Therefore if you use the "don't pre-allocate disk space option", when you look at the actual
file size of the VMWare image after Windows 10 has been installed, it too is only 26GB,
irrespective of the total capacity you assigned to it.

To help ensure the amount of storage used on the C drive does not appreciably
increase over time, I would recommend turning Restore Points to OFF on it.

If your application software is on a totally different partition/virtual drive and you turn
restore points off for the virtual C drive, then it isn't going to "bloat" over time.

Anecdotally those of us that use a SSD for the C drive on a physical
machine to hold the OS but little else will have noted that when Restore Points are
set to off, its storage requirements don't change significantly even over many years of use.

From time to time however, Windows will want to apply updates to the files that constitute
the operating system.

Whilst it is upgrading, it will probably need temporary storage space on the C drive to store the update
whilst still having the current versions of the OS files still present.

It will probably clean these up after reboot. So with that in mind, it might be prudent to be prepared for
the usage to be temporarily two or three times greater than the initial 26GB.

What I would recommend is to make the virtual C drive an arbitrary large value, say 1000GB, do not pre-allocate the
storage on the virtual machine setup and set Restore Points to off on the C drive from within the virtual machine.

With Restore Points set to off, you will of course have some other backup strategy in place, that is, backing up the whole
virtual machine on a daily basis. If something goes pear-shaped, roll back to the previous backup of the virtual machine.

By declaring the drive to have some arbitrary large value, say 1000GB, it gives you the flexibility to move it to a different
physical machine if circumstances change and then the storage capacity is there if for some reason you need it.

I trust you will find this helpful.