Here's the deal:
I have a partitioned ST9320325AS on my laptop set up with GRUB. Yesterday I got a blue-screen while working on Windows 7 and in the automatic reboot attempt I got the 'Operating System Not Found' error message. I rebooted the computer once again and entered the BIOS setup just to see if recognized my HDD - it did. Next step for me was booting a Live CD and seeing if I could repair GRUB or at least check if something changed on the partitions, but it didn't seem to recognize anything there either with blkid, fdisk -l, Test Disk, and not even GParted could see it.
I asked for advice on SuperUser and people pointed me to SeaTools, which was hardly useful in this case, telling me about a connection problem with the cables or power supply. Of course, I tried tightening things up but without luck, since the error persisted.
Here's some data:
hdparm output - http://pastebin.com/KCnmm0Wk
What should I do? Would it help if I bought an external SATA 2.5" case with USB connection to backup my data?