I installed Ubuntu 16.04.3 as a secondary os to my Windows 10 because I need Linux environment for my diploma work. I was silly to only allocate 30 gigs of free space which of course wasnt enough and I had to reinstall Ubuntu. Here's where the fun begins. In windows, I deleted the ubuntu partition and allocated 100 gigs of space for the new install. The next time I booted, grub of course went into grub rescue mode so I inserted a win7 install disk and via command prompt I fixed the master boot record. Now I tried to install Ubuntu again and it fails because Grub is not installed therefore the OS cant boot, so it says. How can I fix this issue?