Dual Boot vs Full Linux

You can download the Windows ISO from Microsoft. The Windows License information is stored in your BIOS, IIRC

Just as pee is stored in the balls, sure. Any computer with a BIOS that did the bidding of Windows like that is automatically insecure garbage. Thankfully it isn't a thing, your license info is stored by Microsoft attached to your account.
- It really is.
  
  sudo strings /sys/firmware/acpi/tables/MSDM
  
  Spec straight from Microsoft: https://download.microsoft.com/download/1/3/8/13818231-a8ad-4fe7-b4e1-a63cbc5d6027/microsoft-software-licensing-tables.docx
  
  An UEFI shell application that can extract it as well: https://blog.fpmurphy.com/2018/01/accessing-acpi-msdm-from-uefi-shell.html
- At the very least try to do some research before posting something both daft and pompous
- Well...
- I just set up a brand new Lenovo laptop today, that came with Win11. I quickly decided Win11 was hot garbage, and installed Win10, removing all partitions and wiping all drives. I never signed into a Microsoft acct on the machine, created only a local acct in Win11 and again in Win10.
  
  When I installed 10, it never asked me for a product key, which had me scratching my head, until I googled and found that it had already activated Win10 home and how I could activate pro.
  
  Long story short, it does appear that newer laptops have the key in their hardware somehow.
  
  Anyway, the writing is on the wall - I can't keep going with Windows. Which led me to lurking here.

You can download the windows iso from windows webpage, but if I remember correctly you have to do it in Windows since it depends on a downloader program. Then you should store the windows cd-key just in case, you shouldn't need it and there are ways to recover it from Linux if this is an OEM machine, but it's always better safe than sorry.

With all that being said, a bit of unpopular opinion now. Why do you want to do that? I kept a windows partition for years because I never knew if I would need it, it was only when I realised I hadn't touched Windows in months that I felt comfortable removing it, and at that time I didn't cared if it could be reinstalled. The reason I'm asking is because if you have to ask about it you probably never installed windows on a machine, so you don't know how to do that, and it's a lot more complex than Linux because Windows needs all of the drivers to be manually installed to work properly, and while Windows 10 is a bit better in finding those drivers automatically it's still a Pain in the ass to ensure it got the correct things and wait the thousands of reboots to apply all updates because updates are cumulative in Windows.

You can download the windows iso from windows webpage, but if I remember correctly you have to do it in Windows since it depends on a downloader program.

It only forces you to use the media creation tool on Windows, everything else it gives you a link to download the ISO.

I kept a windows partition for years because I never knew if I would need it, it was only when I realised I hadn't touched Windows in months that I felt comfortable removing it

I'm exactly the same.
- everything else it gives you a link to download the ISO.
  
  Then that's new, you had to jump through some hoops to get the iso before, I remember just giving up and going to my sister's computer to download it back then.
You can get the Isos from the installer page too installer is just there for people who don't know how to/don't want to flash it themselves
The media creator runs perfectly in wine. But isos are easy to find as well.

I do not know about W11 (using only Linux since 2000) but usually when installing Windows this is going to wipe out your whole disk, including any other os. That is why to have two (three or four) os you should install windows first, then any other os, the opposite is more like...a problem.

Can confirm, Windows does not give a single fuck about anything else you're trying to do, will assume every drive is just more space for Windows and steamroller your entire system lol. Much easier to just let it do what it wants first, and then repartition everything to the correct shape when you install Linux afterwards.
You can install windows to a selected Unallocated Space and it will create its partitions, but if it detects an EFI partition, even in a different drive, it uses that for windows.
- I do not use windows since year 2000. What windows version started that? Remember that there was a windows bootloader that could do this but i did not care to learn about, it was not worth of.

Permanently Deleted

I just want to reiterate that it is a major pain creating a bootable Windows installation USB drive on a Linux or macOS system. It'd be prudent to create it before installing Linux or make sure you have another Windows computer accessible to you to avoid some headaches if needed.
- Ventoy, Ventoy, Ventoy .

If you wanna dual boot, I'd recommend installing windows 1st, Linux 2nd. The windows installer has a very high chance to mess up the Linux bootloader, even if you tell it not to touch that particular partition

Keep windows on a second drive and instead of dual booting, open the windows OS in a virtual machine inside linux

I tried that once, technically possible but it wouldn't let me login on the install I had been using long term previously (seemed fine on a completely fresh install)

Need windows little enough that I've just put my existing license in a fresh VM instead
- Oh weird, thats how I have my system setup, and Ive reinstalled my OS a few times. the VM dualboot part worked on both arch and Debian but I'm not familiar enough with debian toi get GPU pass through working
How does one set this up? Just create a blank VM and pass the drive through?
- I set mine up a while back, I can't remeber if I installed windows 10 on bare metal or in the VM. I remember I tried both, I want to say installing in the VM worked better. But what I do, is first set up KVM/qemu with virtual machine manager. Then IF YOU DONT HAVE WINDOWS ALREADY wipe the drive you want for windows. I usually just wipe and leave it as free space and not create a partition. Then in virtual machine manager, create a new virtual machine. Use local install media as the install option, select your windows ISO, then instead of 'create disk image for virtual machine', you check 'select or create custom storage and type in /dev/nvme1n1 or whatever the drive address is. check the customize before install and make sure its using UEFI instead of BIOS.
  
  IF YOU ALREADY HAVE WINDOWS INSTALLED, open virtual machine manager, add new virtual machine, manual install, select or create custom storage, then type '/dev/nvme1n1' or whatever your address is. Check the custumize configuration before install and make sure its using UEFI instead of BIOS.
  
  for both you'll want to install the KVM windows drivers you can find them on github

Perfect, thanks a bunch for the replies! Seems I'll be trying to go full Kubuntu soon then, now that Steam's Proton is doing so well!

I’m kind of doing something similar. I built a machine from scratch and installed arch Linux on it. Now I want to see if i can plug in a hard drive from an older computer that already had windows on it. Then dual boot from that. Not sure what I’ll run into but I’m probably going to try it this weekend.

should work just fine just look at the wiki for os-prober to get it in your grub menu
I’m running that and I don’t have any issues. I just have to go to bios instead of using a boot manager.
- if your using grub you just need to install os-prober and re build your grub config and then you can boot windows from grub even on multiple drives

What desktop was it? I'm probably not getting anything anytime soon, but I'm curious for future

I got a lot of great advice on another thread recently (which I still need to go through) on how to get the dual boot going, would be nice to have it be like that out of the box.

Also one thing that might be relevant, sometimes reinstalling windows may cause issues with extra features tied to a particular version. This is second hand experience, a friend replaced an SSD and could no longer use certain features (bitlocker?) because they were only on the pro version of Windows. Somehow they were enabled before.

So I guess it's less of a problem and more of "you may lose things that windows decided you weren't supposed to have"

is it possible he forgot to select pro in the install menu a pro license will activate home no problem