I had two hard disks. One is internal, 320GB, all NTFS, where Windows 7 is installed in a ~20GB partition. The other is external, 160GB, where I have installed Fedora. Now when I had installed Fedora I completely detached my internal drive so there is no relationship between internal drive (having Windows) and external.I had installed Fedora17 32bit on my 168GB external drive & I was loving it for about 2 weeks. However something bad happened and now whenever I boot via external drive 'Grub Error, unknown filesystem' appears and I can't proceed. I had been using following partitioning layout: (all as ext4)/boot 300mb/ 30gb/opt 9gbswap 2gb...rest as NTFS (to be used universally)The following application (under Windows) has the feature of even identifying Linux based filesystems but as you can see everything is corrupted.Now I can absolutely recal that I did two things that I believe may be the source of corruption & I urgently need help in troubleshooting it.First thing I did was to apply this tutorial. I know this may appear stupid to apply Ubuntu way over Fedora but I was close to solving it... After applying this tutorial I did log-off several times perfectly but didn't reboot!This may well be the probable reason of corruption. As I said I had one NTFS drive so that I can use it even under my Win7...so I logged on to my win7 as always. I had to do some data transfer from my windows to that NTFS partition but I saw some folder namely ./install or something like that those may have been created by Fedora but I (being silly) just deleted them I don't know whether they were important or not but after this I shutdown my Win then booted via external drive and first time my Fedora took me to Grub selection menu but failed to start I can't recall comprehensively but it asked me to press Ctrl+D or enter root password for recovery I suppose.I panicked (because I have installed many educational application in my Fedora) and just restarted via pressing Ctrl+Alt+Del then the final dreadful error 'Grub error Unknown filesystem`.I booted via bootable USB the same O installed Fedora with, the following screenshot is of application 'Disks'It doesn't recognise anything except the swap and NTFS (labelled khanz) partitions. I even can't retrieve my Maple/Matlab licences from these (as of now)  unknown filesystems?I was told that I should have a separate /boot partition because that avoids what I am facing presently, but that didn't go well either.
Failed to boot Grub Error Fedora 17
fedora;boot;partition;grub