For some reason, after installing Ubuntu, Windows stopped seeing one of the disks

Question

Hard disks

Good afternoon, I recently installed Ubuntu 14.04, which demolished the Windows bootloader for me and used one ubuntu for two days, then I thought of updating ubuntu, and the update, apparently, was also the bootloader. The bootloader started seeing Windows 8.1 on me. But here's the thing, one of the disks (I have two hard drives on each with five partitions, Ubuntu is on one hard drive, Windows 8.1 on the other. You can theoretically install two more systems, but I'm not talking about that. Windows stopped seeing one of large sections where all the information is stored (in this section, music and programs) And it does not see because with each new reboot this section loses its name letter (Disk K:) That is, the name remains as I called it there, but the destination letter disappears, every time after loading Windows, you have to open the Acronis disk director and assign a letter to this partition. After that, the disk starts working. Such is the story. I tried googling and didn't find anything similar.

Answer 1

The disk system still sees it without a letter, and the rename point is not active