Questions about dual boot with Windows 10 and Windows 7

Hello TenForums, first post from a forum lurker new to Windows 10. I've been using Windows 7 Home for years and found Sevenforums very helpful just like this forum. I have read this thread and other tutorials about this topic on other sites/blogs and still have a few question before committing to dual boot.

Very recently I installed Windows 10 pro to a new/separate SSD via USB(UEFI/GPT/etc), Windows 7 was installed non-UEFI(MBR). I did something potentially stupid long ago by using EasyBCD to get rid of the System Reserved partition on Windows 7. I also have 2 more internal storage drives. I have not yet used Windows 10 with the other drives connected and this is obviously inconvenient. I do have each drive backed up via Macrium just in case the dual boot goes wrong once all 4 drives are connected. It would be no problem to wipe the Win10 drive and reinstall, but I would rather not reinstall 7 if possible.

If all 4 drives are connected and boot via UEFI/OS to Win10 (GPT) will it harm the Win7 boot/MBR, and if not, will I get the Win10 boot manager?

Would it help to reinstall Win7 via UEFI first, then reinstall Win10 to the other drive while running 7 via setup.exe inside the Win10 sources folder?

Assuming dual boot requires this via elevated command prompt : "bcdboot X:\windows /X /addlast" (X=the other Windows drive), from which OS should it be done?

Finally and most important, if I get dual boot running without the need for switching in BIOS/UEFI, GRUB, or other bootloader, what is the best way to share the folders/files on the 2 storage drives between both operating systems?

This computer is not on a network/homegroup, doesn't share anything with other computers, and has no other users (other than 2 operating systems = 2 users). I do have my Steam library on one of the storage drives but do not expect to use it from both operating systems since the gamesaves are all over the place, often in odd places on the C (windows7) drive, and that cannot be changed. I have not moved any default Win7 user files, libraries, etc.(the "MY" folders), rather the Win7 libraries include (point to) folders residing on the other drives.

Apologies for the long first post.

As long as your Bios has a UEFI & Legacy option, you can go back and forth from 7 to 10 without any problems. At least I can.

But I made an image of W10 after I installed installed it using UEFI and reinstalled using Legacy mode and MBR, I see no point in using UEFI.

I also never leave both drives plugged in, I use 7 or 10 and switch whenever the mood strikes me.

I run my games from 7 because of the constant updates and subsequent clean installs of Windows 10.

AddRAM said:

As long as your Bios has a UEFI & Legacy option, you can go back and forth from 7 to 10 without any problems. At least I can.

But I made an image of W10 after I installed installed it using UEFI and reinstalled using Legacy mode and MBR, I see no point in using UEFI.

I also never leave both drives plugged in, I use 7 or 10 and switch whenever the mood strikes me.

I run my games from 7 because of the constant updates and subsequent clean installs of Windows 10.

Thank you for responding, but I already dual boot by disconnecting the unused OS drive, if that can be considered dual booting. My BIOS has both UEFI and Legacy, but there should not be a need to switch if both OS are UEFI, or both Legacy. I would like to have the ability to switch OS at least once a day. Leaving the case open and unplugging drives that often is asking for trouble in this house. It would be easier to use docking bays for OS drives but using the Windows 10 bootloader would be ideal in my situation. Ideally, there should be no need to go into BIOS anymore once this is setup, as it is in the tutorial.

There is a tutorial here for dual booting 7 and 10, but there is no tutorial for sharing internal files/folders/drives on a dual boot system. If there is, I can't find it. Should I treat the internal non-OS storage drives like network drives to be shared via group/specific user permissions, or is it the same as giving read/write permissions to other users on the same OS even though it's a different OS on the same computer? Some guy named Bob on 10 can't be considered the same Bob on 7. If I don't give permissions to Everyone how can 7 and 10 tell which Bob is Bob? Do I need to use different names for myself on each OS? That would be split personality time, I might use different names on various forums but this is my home PC.

Anyways, I don't plan to use Steam on more than one OS, the gamesave locations alone make it too complicated. I just want to edit documents, rename files/folders, edit videos, play media (easiest), without making duplicates and syncing. Basically, an internal network with read/write permissions. I don't need or want one OS drive to touch the other, only the storage/media drives. I understand shared folders on networks, I understand dual booting Linux and Windows, I just don't understand internal file sharing in a dual boot Windows system.

Thanks again. I will clone the 7 drive, the others are imaged via Macrium to external drives, and the next step is to reinstall 7 via UEFI/USB for the GPT format to match the 10 boot. Missing files after program installs on 7 can be copied from the clone. More info on file sharing would be helpful.

Yes, there is no need to switch anything if both are UEFI or both are Legacy.