I think the hdd has gone kaput. First check whether the hdd is properly detected by System BIOS. If it is then it can be a case of partition loss only, otherwise dude, you're out of luck, prepare to purchase a new one. If its partition loss, try various tools that are available both for free and the paid ones. I once lost my partitions while installing linux, i used the Ultimate Boot CD, it contains a utility called testtool which is a text ui based one, but works very nicely.

Try and post here the results.
And yes do check the data and power cables of hdd also.