I have a shiny new machine (Lenovo P53). It comes with a factory-installed Windows. I don't need Windows, and will install Linux. OTOH 4-5 years from now I could get a newer machine and pass this one to someone who prefers Windows. So I want to be able to put back Windows on it later on.
There is an obvious easy option: swap the boot drive with an empty one and keep the Windows one, but that would be quite expensive since the boot disk is a rather big SSD and I'm not willing to pay that price for a copy of Windows.
So my other options are:
Use an external Windows installation disk
In other words, I wouldn't need to do anything with the current machine, just find a W10 ISO somewhere and archive it (and maybe complement it with specific drivers). But is this a real option?
Save the current windows install
This by itself is two sub-boptions:
Save partitions
Can I save the Windows partition alone or should I add the UEFI boot partition? How would I restore them properly on a new disk? The Windows partition is about a terabyte, but is mostly empty, can I shrink it first? Or just hope it will compress well?
Save the whole drive
How can I make sure it compresses well (should I use a TRIM commands first)? But can it be restored on a slightly different disk (5 years from now, current disk could have been replaced)?
Keep the recovery partition
There is a one GB partition (aout 60% full) called WinRE_DRV that the Windows partition manager labels "OEM partition". Is this a recovery partition? Can I save/restore it? Can I just leave it there (1GB isn't much) and hope that the BIOS can still use it?