I don't have install media. I want to be able to reconstruct my hd in the event of a bad news occurrence.

In that case cloning the disk is the only real option. Using Clonezilla, for example. But be aware you would need to activate Windows if certain hardware components change : the mainboard, for example. You should be OK with a new disk, more memory, perhaps a new graphics card.

I believe Windows 10 and probably 11 will do a full system image backup with native tools? I've read that it's possible to use rsync from a stand-alone linux partition or even 'Windows Subsystem for Linux' (WSL.)

https://pureinfotech.com/create-wind...-image-backup/
https://thedatafrog.com/en/articles/...c-windows-wsl/

You can obtain a multi-edition Windows 11 ISO from Microsoft themselves

When it comes to Windows partitions, I have always used dd. Yes, it is comparatively slow. Yes, it wastes space. But the NTFS specifications have never been publicly released, so a bit copy seems the only safe option.

Physical install media for Windows hasn't existed since the Windows 7 days. From Windows 8 onwards, retail purchasers of Windows receive a card (about the size of a credit card) with a serial number on it and a link to the download site.

As per Mr. Lally, you can download an iso from Microsoft and put it on a Ventoy USB stick. You could put one of Eric's Slacware live isos on there too for the ultimate rescue USB stick.

I have had poor success restoring bit copies as you need an identical disk in every way. I don't mind it being slow. It's not like I have to sit and watch it in these days of multitasking.

OK Guys, thank you all very much for your help, but there's been a development.

I tried to get the copy of Windows from M$ themselves as per post #19, but it seemed easiest to do that from Windows, as the M$ site was asking questions I couldn't answer. It's best to get all your ducks in a row doing a bare bones install, which meant frequent recourse to search engines, whereupon windows suddenly downed tools and wanted me to back up to my (non existent) cloud account.

The thought occurred to me that I was getting into a hole, so I should stop digging .
When am I going to wear out a windows partition that isn't being used? I reckon it won't be soon.
What harm if I can't restore windows? Er, none.
Do I want to learn about WSL? No, life's too short.
Do I want to jump through the rather extensive set of hoops that M$ has set up before I can do a barebones install? Not likely.

So I left it there and apoplogies for any time wasted on your part. Windows is badly in need of a 'middle finger' button, but I don't expect that to be fixed any time soon.