I recently converted my external hard drive from FAT32 to NTFS using the Command Prompt. Everything was working fine, I copied a 7GB file to it and everything worked. The next day I switched on my PC, I couldn't and still can't find my external 1.5TB hard drive by my computer.
I have about 500 to 800 GB of data on it that I really don't want to lose. Its a Iomega Seagate Freeagent HDD. Has no switch, it switched on automatically, don't know if that helps.