Dual-Boot Win7/Win10 on seprt HDD's - Both HDD's detected, 7 wont boot

I have a dual-boot setup on a Dell XPS 8900 that I've had since Feb/March. The dual boot setup has been working fine, with zero issues since then, then this week I just booted into Win7 a couple days ago and it ran chkdsk automatically, erased some files, restarted, and booted into Win7 fine. I used my OS with no issues and shutdown. But this morning I tried to boot into Win7 and my system can't find the operating system.

I bought the computer from Dell with Win10 installed on their standard 1TB HDD and added a WDC 2TB HDD and installed Win7 in Legacy. I can still boot into Win10 with no problem in UEFI, and while using the OS I can see my other Win7 HDD, all the files are still there and I can access them. My system can even detect Win7 in UEFI mode and will begin to boot to that OS (but of course, freezes at the logo screen because Win7 won't run on UEFI). The BIOS detects both HDD's and diagnostics says that everything's fine with both, but when I try to boot into Win7 in Legacy mode I get a no boot device error.

I've run the Windows7 install CD to try to run diagnostics and repair startup files, but all the diagnostics, including chkdsk, come back with zero issues, except 0x01f and 0x495 which only says that something was changed, but nothing specific...

I can't tell if the problem is with my startup files, MBR, or BIOS...

I've already backed up my Win7 HDD, but I'd rather not have to reinstall Windows cuz all my gaming stuff is on that HDD...

Can anyone help?

Thanks Thrash, I've never enabled fast start since I setup the dual boot system. And I've never shared files from one disk to another or accessed them that way, other than backing up my files on Win7 to an external HDD from Win10 today.

Either way, could you tell me a little more about the mobile rack you suggested?

And Thanks

ThrashZone said:

Hi and welcome to SevenForums,
Dual booting with all hdd's connected can be problematic
I personally use one of these to simplify the task after many mishaps dual booting on the same disk.... I never found a better/ more reliable way other than this,
Amazon.com: Vantec 2.5-Inch Dual Bay Trayless SATA III - 6G Mobile Rack (MRK-225S6-BK): Computers & Accessories

Installing each os you'd want to remove the other disk completely so each os would have it's own boot loader.
Even though 10 can access win-7 I would not do it this will often trigger check disk to run in win-7.
Not to mention Fast start in win-10 will trigger it too
Fast Startup - Turn On or Off in Windows 10 - Windows 10 Forums

So yes disable fast start in win-10 is a must do.
Also for good measure disable fast or quick start in your bios too.
I would not share data disks either.

So i see. Someone is using this method to dual boot.
I agree that this is the most safe way, i use it when i am using Desktop without problem.
But for laptop, i do may have a similar way then this.

ThrashZone said:

Hi,
A laptop I would convert the dvd tray into a ssd holder :)
Just about everything is going usb anyway I barely ever use the dvd/cd drive anymore.

If you ever played with Linux you might know the grub is a biotch to deal with and or get rid of :)

Thanks.
Already bought this DVD tray for SSD holder.
Already having too many external cases and internal HDD and Ext HDD (more than 10+ HDD for both)
Later may have to get USB DVD, as i usually do run other program outside, although seldom use optical drive.
Such as Mini Tools Partittion Wizard, and another similar program O&O DiskImage 4.

Only on Windows, but never on others such as Linux.
Wanted to try, after all too many HDD, but not too sure, which required further reading.

Jmarc said:

I have a dual-boot setup on a Dell XPS 8900 that I've had since Feb/March. The dual boot setup has been working fine, with zero issues since then, then this week I just booted into Win7 a couple days ago and it ran chkdsk automatically, erased some files, restarted, and booted into Win7 fine. I used my OS with no issues and shutdown. But this morning I tried to boot into Win7 and my system can't find the operating system.

The problem may lies in what chkdsk do and which files were deleted, i assumed you let chkdsk to do that.

Never trust chkdsk to do things for you, or any program to handle it without you knowing.
You may know, but anything could happen, as computer use LOGIC, and you may assumed everything is in order.

This failure to boot did happened to me.
I was using Mini Tools Partition Wizard CD bookable and do the cloning.
When finished cloning, restart the laptop, the system Failure happened.
Then i remember something, which this MTPW did more than cloning.
It remove the Boot option from the 1st partition 100MB.

There is another option for dual boot.
Any OS partition indicated "Active" & with boot & system files, will and may boot from that partition.
This too happened to me, which is very long ago.
A program add another partition as "Active" partition which also have the boot & system files.

So, you need a program that can do as other OS do, but to not to run in Windows mode, do check these Active, Boot, System, etc which able to boot.

You can try to use MTPW CD (&or other similar) to boot up, which i did reset the boot.

It was a brand new drive, it shouldn't have been failing, well not brand new but close.
Yes, I did back up the data and I'm going to reinstall (it's Win7 64bit, btw).
I did not detach the Win10 disk before I installed, maybe that's what caused the problem...
I switched UEFI to Legacy mode in BIOS and on startup, after POST I got the option of Windows 7 or 10 from the Boot Manager...
((ex. http://winsupersite.com/content/cont...l_dual_038.jpg))
This was automatic, I did not have to go into BIOS to choose OS.

Do I need to clear the old boot record from my computer before I reinstall?