I have a problem when I try to install windows on my second hard disk.

I'm using a pc portable and Actually Ubuntu 22.04.2 on my first hard disk but I have also Ubuntu on my second hard disk. To install windows I have an external hard-disk Seagate 2tb. I've tried to read other questions but they are incomplete or difficult (for me) to understand.

I have actually downloaded the windows.iso but when I try to copy it on the hard disk I receive an error message telling me: Error splicing file: File too large1

I ask you please to write to me all the steps that I have to do, I need them to work and I have a lot to do.

if possible i would like to do:

1. remove Ubuntu from second hard-disk
2. install windows 10 on my second hard-disk (indicate to me the best win key to buy)
3. have Ubuntu on my first Account
4. Have the possibility to choose which account I can run at the start

secondary importance: 5. Solving that error message that doesn't let me update (sudo apt-get update)