dual boot - GRUB can't load Windows 10

I have a laptop with two disks. On the first one I had windows 7 and on the second ubuntu 14.04. Grub is installed on the second disk. Everything was fine but after upgrading to windows 10 (which obliged me to set the first disk as the default boot disk), grub can't load windows. Now when I boot my laptop, it starts automatically windows 10. When I want to use ubuntu, I have to press F9 and boot manually on the second drive. If I set the second drive as the default boot disk, grub loads on the startup. If I select ubuntu it starts normally but if I select windows it can't boot. The error message is saying something like windows\system32\winload.exe was modified or there was a hardware change. Any help to have a working dual boot?

You may try setting the second disk as the default boot, boot into Ubuntu and do the following:

• Open a terminal and run:

sudo nano /etc/grub.d/40_custom

It will open a text editor with some code. Go to the end of the file and add the following lines:

menuentry Windows 10 (disk 1) {

set root=(hd0,msdos1)

chainloader +1

boot

}

Hit Ctrl+O and then ENTER. HitCtrl+X. Now run:

sudo update-grub

And reboot. Make sure the second hard drive has boot priority. When GRUB shows up, select "Windows 10 (disk 1)" and hit ENTER.