Windows 7 & 10 dual boot question(s)

[omnescient]

When first installing Win7 Pro x64 to my desktop a few years ago, it was done in BIOS/CSM/MBR mode.
I want to keep W7, and also install W10 Pro, with a view to phasing out W7 (by the time all support stops in 2020), but have each on a separate SSD.
I'm considering 3 possible scenarios:
1. Dual boot 7 & 10, both as CSM/BIOS/MBR (W10 install only).
2. Dual boot 7 & 10, both as UEFI/GPT, which would require me to (first) reinstall W7.
3. Install 10 only as UEFI/GPT, and select the os disk from the firmware boot menu.

My data is on a separate MBR HDD, and backups on external MBR HDDs.
Both 7 & 10 are full 'retail' versions (W7 disc/W10 USB)

I'm aware of issues with firmware Secure Boot & os Fast Boot, Windows Update problems regarding re-installation of W7, and would be disconnecting/disabling other drives during os installation.

Any advice as to which (if any) of the above scenarios is preferable, and other potential issues you can foresee would be appreciated.

 

[ThrashZone]

Hi and welcome to SevenForums,
Yep many people are doing the same thing thinking they can keep both 10 and the upgraded qualifying os,
M$ will eventually deactivate the key and show Not genuine messages.

After upgrade you have 30days to use 10 and be able to revert to 7 or what ever
But you must use win-10 recovery to get back to the prior os
Then you can restore a system image to before you upgraded.

If you want to do as you say you might join the insiders program
Use a M$ account as login/ outlook.com/ hotmail/..
M$ still requires a qualifying os activation key but may not eat it until July 30th when the free upgrade offer expires.

 

[AddRAM]

If you do a dual boot of 7 and 10, everytime you switch the OS it`ll run a disk check, it`s a PITA.

Don`t even bother with the dual boot, put 10 on a separate machine.

There`s a way to fix it, I`m sure someone will let you know, I think you have to hide one OS from seeing the other.

 

[ThrashZone]

Windows verifies the activation key as soon as internet connection is made

 

[omnescient]

Thanks for the replies.
I should start by correcting myself. Does a non-system/data disk have a boot record? Obviously not, so either it was late, or I was talking out of the wrong end as usual.
(wipe/format/re-install neural OS)
Data is on an internal HDD with 4 primary NTFS partitions. Backups on similar external HDDs.

@ThrashZone
Are you saying that this product:
Windows 10 Professional 32-bit/64-bit English International: Amazon.co.uk: Software
has to be installed and activated as a Windows 7 upgrade?

@AddRAM
So you wouldn't advise reinstalling W7 in UEFI mode and then installing W10 for dual booting?
Or installing W10 in CSM mode for dual booting?
I can see how option 2 would be a PITA.
I assumed that option 1 or 3 in my original post would accommodate a dual boot without a firmware selection; maybe I've got that wrong.

 

[ThrashZone]

No that one can be clean installed without a win-7 tied to it

There are also 10 home or pro single 64 bit or 32 bit versions that are cheaper if you know which version you need
Having both versions is a waste.