I accidentally deleted my Ubuntu 14.04LTS partition lately (with Arconis Disk Director under Windows 7), now I cannot boot either into Ubuntu or Windows. After I start my computer, I will be brought to the Grub rescue mode. Typing "ls (hdX.msdosY)" for any X and Y gives me the response "Filesystem is unknown". I tried reinstalling Ubuntu with a USB stick, but as soon as I hit "Try Ubuntu without installing" or "Install Ubuntu" in the Ubuntu installer boot menu, the computer restarts. What can I do? Is it possible for me to recover my Ubuntu installation, or at least boot into my Windows installation?
More info on my Ubuntu installation: My laptop was preinstalled with Windows 7, and then I installed Ubuntu alongside Windows. I have only one hard drive and I created a 100 GB logical partition for Ubuntu.
More info on how I deleted my Ubuntu partition: I was showing a friend how to expand the Windows C: drive with Arconis disk director. My Ubuntu partition uses ext4 file system so it's shown as blank in Arconis. Without much thinking (since I have a few other unused partitions so seeing a blank partition didn't alarm me), I showed him how to delete that partition and use the released disk space to expand C:. Later when I was going to get back to work with Ubuntu, I found myself unable to boot! Neither Ubuntu nor Windows!