Dual boot with Windows 7 stopped working - Ask Ubuntu

i installed ubuntu 16.04 lts few days ago on brand new ssd, empty (sda), , kept windows 7 install on separate ssd (sdb). grub installed (i guess on sda?) , after installing ubuntu, select system start, grub menu. tried right after installation, , did work fine.

but morning, when tried restart windows grub menu, got following error message:

error: no such device: 2844473f44470f4e. setting partition type 0x7  press key continue... 

now cannot start windows system anymore. idea has gone wrong, , how fix that?

additional info may help:

the initial fstab after ubuntu install was:

# /etc/fstab: static file system information. # # use 'blkid' print universally unique identifier # device; may used uuid= more robust way name devices # works if disks added , removed. see fstab(5). # # <file system> <mount point>   <type>  <options>       <dump>  <pass> # / on /dev/sda1 during installation uuid=27e8f423-5046-4bf4-8bf6-3ca19a440e9c /               ext4    errors=remount-ro 0       1 # swap on /dev/sda5 during installation uuid=a123385a-2e28-45da-a699-574f26e43b54 none            swap    sw              0       0 

which changed (to add network drive) into:

# /etc/fstab: static file system information. # # use 'blkid' print universally unique identifier # device; may used uuid= more robust way name devices # works if disks added , removed. see fstab(5). # # <file system> <mount point>   <type>  <options>       <dump>  <pass> # / on /dev/sda1 during installation uuid=27e8f423-5046-4bf4-8bf6-3ca19a440e9c /               ext4    errors=remount-ro 0       1 # swap on /dev/sda5 during installation uuid=a123385a-2e28-45da-a699-574f26e43b54 none            swap    sw              0       0 # added on october 25, 2016, following instructions @ http://ubuntuhandbook.org/index.php/2014/08/map-network-drive-onto-ubuntu-14-04/ //192.168.0.1/data                         /media/z        cifs    credentials=/home/jfs/.smbcredentials,iocharset=utf8,gid=1000,uid=1000,file_mode=0777,dir_mode=0777   0       0 

after trying boot-repair (see comments, did not far), report can found at: http://paste2.org/aveadskx

fyi, fixed problem fixing boot sector of drive on windows installed (sdb). used "windows repair disk".

i guess issue came grub having changed on windows drive (maybe during grub update) not sure...

step step instructions:

1. i got repair disk version of windows (in case 7, 64 bits). if have one, use it. if don't, can use windows 7 computer burn 1 (see e.g. https://www.lifewire.com/how-to-create-a-windows-7-system-repair-disc-2626301)
2. i disconnected linux drive (sda), prevent writing on during process.
3. i configured bios start on cd drive.
4. i booted on repair disk, , chose option start "dos" command prompt.

5. i ran 2 commands:

   bootrec /fixmbr bootrec /fixboot 

6. i checked bios make sure computer boot on sda first (linux drive grub), , sdb lower priority (windows).

after that, reconnected linux drive. can use grub boot on 2 systems. configured linux mount /dev/sdb read prevent linux writing windows drive in future.