I have installed Ubuntu 15.10 and Windows 10 successfully on my laptop. Earlier I was given a choice to choose which OS to load via gnu grub. I remember I accidently clicked some buttons (then it went to maybe edit gnu grub or etc., I was trying to swap Windows and Ubuntu's position). Now I no longer can choose which OS to load (it boots directly to Windows), but I found a workaround: When the laptop starts I keep pressing Esc and then I press F9, then I get a choice again but maybe in some BIOS style. Also I can't access Windows files, I get this error (maybe because I stopped Windows' booting in between):
Unable to access “Windows”
Error mounting /dev/sda4 at /media/aditya/Windows: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000" "/dev/sda4" "/media/aditya/Windows"' exited with non-zero exit status 14: Windows is hibernated, refused to mount.
Failed to mount '/dev/sda4': Operation not permitted
The NTFS partition is in an unsafe state. Please resume and shutdown
Windows fully (no hibernation or fast restarting), or mount the volume
read-only with the 'ro' mount option.