Data Recovery cases and failure symptoms

Drive is not shown in BIOS drive table
Drive is shown in BIOS drive table with a wrong, garbled or generic name
Drive is making repeating, continuous, unusual noise on startup
You cannot hear the usual spin-up sound from the drive
You receive "Operating System Not Found" message on startup
Windows 2000/XP crashes on startup when the problematic hard disk drive is connected to the computer
When you click on the drive letter in "My computer" the message is displayed "Disk is not formatted". "The disk in drive <drive letter> is not formatted. Do you want to format it now?"
You accidentally reformatted the volume, possibly to another filesystem
You deleted the important file(s)
You reinstalled the operating system onto the volume containing important data
The process of merging or resizing the partition has crashed
Drive was retrieved from fire or water
Drive was dropped when it was on or off
Drive in USB enclosure is unreadable after unsafe unplugging from the PC
Drive was subjected to electrical shock, wrong polarity plugging or lightning strike