(Solved) Grub fails to boot into Windows 7, but Windows 7 boots normally

[Benches]

A few days ago I attempted to install Linux Mint 19 XFCE, for a dual boot with Windows 7 It worked, and I can boot into Linux Mint properly, but when attempting to boot Windows 7, it gives the error "0xc0000098: The Windows Boot Configuration Data file does not contain a valid OS entry." However, when I enter the BIOS (I don't have UEFI) and directly boot into the drive that has Windows 7 on, there are no problems at all; it boots perfectly. So what's the deal?

Some information about my 3 drives:
/dev/sda has 2 partitions, and is the location of Windows 7.
/dev/sda1 is 100mb Windows system reserved, and /dev/sda2 is 1TB and contains Windows installation and lots of other files.
/dev/sdb has 2 partitions, one extended, and is the location of Linux Mint.
/dev/sdb1 is 200gb file space, but is also where I installed Grub (iirc), and dev/sdb2 consists of dev/sdb5, 6 and 7. (I'm not sure what happened to 3 and 4?)
/dev/sd5 is 20gb mounted at root, /dev/sdb6 is 4gb swap memory, /dev/sd7 is 270gb mounted at home.
/dev/sdc has only 1 partition, dev/sdc1, which is, you guessed it, 160gb of more file space.

Any help with this issue would be awesome, and apologies if this post is badly written or not specific enough since it's like 5am.

[michael louwe]

@ Benches, .......

.

.
Some users prefer your inadvertent situation, ie boot Win 7 or LM via BIOS Setup, because Windows Update can bork the LM Grub bootloader and/or system. This is even more crucial when dual-booting LM with Win 10 which forces auto-updates/upgrades.

IIRC, if you want to have a Grub Menu where you can boot either LM or Win 7, you need to do a sudo update-grub while running LM. Then reboot.

There is no /sdb3 and /sdb4 when you use logical partitions, ie not as Primary partitions. Because MBR/ms-dos disks are limited to 4 Primary partitions, logical partitions are often needed, especially when dual-booting on a single disk/drive. In your case, you do not need to create logical partitions for your LM system, ie Root(/), Home and Swap are only 3 partitions on /sdb = they can all be created as Primary partitions.

[Benches]

...you need to do a sudo update-grub while running LM...
There is no /sdb3 and /sdb4 when you use logical partitions, ie not as Primary partitions...

Thanks a bunch for the help and explanation! Works a charm.