Win 10 Win 7 Dual Boot Not Booting to Win 10

Dell 7010 Win 10 and 7 Dual Boot PC.
I have a Dell 7010 set up as a dual boot machine. C drive is Windows 10 and D drive is Windows 7.
Windows 10 is the default OS, so if I do not select Win 7 when the selection screen opens, it used to start the Win 10 automatically. The Win 7 OS still functions.
For a week or so it just sits at the selection screen and never starts WIn 10, even If I click on the Win 10 button.
I looked at the particions using Disk Management and noted that C drive (Win 10) shows Healthy (System, Active, Primary Partition) and D drive (Win 7) shows (Healthy, Boot, Page File, Crash Dump, Primary Partition).
It strikes me that the C drive should show Boot and not the D drive? Am I correct? If this is the case is there a simple way to correct this?
Thanks in advance.

Samuria said:

Normally the quickest way to fix this is down Macrium Software | Reflect Free Edition that has a built in function to fix boot files give that a go

I'll try that, I have it installed.

Megahertz said:

The partition letters are assigned by the OS it is booting.
If you boot Win 7, the Win 7 partition will be C:.I did not know that.
If you boot Win 10, the Win 10 partition will be C:. I did not know that.
Please post a whole window Disk Manager image of your drives. Don't forget to expand the columns so we can read them. How to Post a Screenshot of Disk ManagementIf you have a MiniTool or AOMEI Partition use it instead or Windows disk manager.

See attached picture

I also noticed tonight that the PC no longer opens the OS system choice window, it goes straight to Windows 7. I usually don't sit and watch it start, as I mostly use windows 10. Errr...

If you boot Win 7, the Win 7 partition will be C:.
If you boot Win 10, the Win 10 partition will be C:.

@Megahertz Often, but not always.

Assuming your win7 os is the same bit version as your win 10:

Open an administrator command prompt and type ( or copy and paste bolded lines from below)

cd /d c:\windows\system32
(then press enter)
bcdboot c:\windows
(then press enter )

That 500gb seagate is awfully slow. Have you considered upgrading to a sata ssd or even an nvme?

SIW2 said:

Assuming your win7 os is the same bit version as your win 10:
Open an administrator command prompt and type ( or copy and paste bolded lines from below)
cd /d c:\windows\system32
(then press enter)
bcdboot c:\windows
(then press enter )

I'll try that later today, thanks and I'll post back. Both OS's are 32 Bit.

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SIW2 said:

That 500gb seagate is awfully slow. Have you considered upgrading to a sata ssd or even an nvme?

I have been considering upgrading the 500Gb to a larger drive (I have a 1 and a 2 TB HDD available) to give me more elbow room. I am curious how you figured that it was slow from the screen shot I posted. Maybe you looked up the specs on the drive?
Stay safe,
Peter B.

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SIW2 said:

Assuming your win7 os is the same bit version as your win 10:
Open an administrator command prompt and type ( or copy and paste bolded lines from below)
cd /d c:\windows\system32
(then press enter)
bcdboot c:\windows
(then press enter )

They are both 32 bit.
I did this but it failed, see picture.

You mistyped.

it should be cd /d c:\windows\system32

and

bcdboot c:\windows