Installed Ubuntu in parallel with the Windows but don't want to break Windows.
In superuser mode in live system:
mount /dev/sdX /mnt
# sdX indicates the partition where Ubuntu is installed (do not touch windows partition) .. to know about partitions of ur hard drive, use “fdisk -l” or lsblk command
chroot /mnt grub-install --target=i386-pc /dev/sda os-prober grub-update grub-mkconfig -o /boot/grub/grub.cfg reboot
Remove live system media once the system poweroffs.
This should solve the issue.
If you are not able to make a live system, then from grub command line:
ls set root=(hd0,msdosX) # you should know which partition the Ubuntu is installed linux /boot/vmlin (press tab) root=/dev/sdaX initrd /boot/initr (press tab) boot
This shoud resolve the issue.