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Initial state: dual boot laptop to either Windows 7 or Ubuntu.
What I tried to do: change my partition of Ubuntu to Ubuntu-Mate.
First problem: first booting for the installation worked fine, but I didn't create a partition with the free space obtained from the previous one.
What I tried to solve it: I restarted the computer and unplugged the usb in order to create the partition in Windows.
What really happened, and final problem: grub rescue is displayed, no matter what boot source used. (Edit 3: I wanted to gain access to my Windows partition, so that I could rearrange my partitions)
Thank you very much for any suggestion.
Edit: I've tried using a bootable Ubuntu usb to get the Boot-info, but it keeps giving an error: "unknown filesystem".
Edit2: I've tried via Boot-Repair-Disk, but even so it doesn't work, to check whether the iso is correctly burned, I'll try it in another computer.