Is the drive external or internal one? In both cases, the troubleshooting steps are almost identical.
Does the drive even power up? In case it doesn't, you need to connect it with a different USB(SATA and power cables if internal) cable to a different port. Trying different cable/s is a good idea even if the drive seems to be powering up just fine.
Is the drive recognized by Disk Management and how?
- In case the drive is not recognized by Disk Management, and you've tried changing cables/ports, then it most probably dead.
- In case the drive appears under Disk Management but has damaged partitions(unallocated) or file system, you may need to use some kind of data/partition recovery software in order to retrieve the data.
Does the HD make a clicking or scraping sound? If so, you're out of luck and it'll cost you an arm and a leg to recover anything from it. You can expect to easily pay $500 (at least), provided it's a complete hardware error. If this isn't the case, what you need to do RIGHT NOW is disconnect the disk. From there, we'll proceed, but you ought to answer my question first.
In case you've tried attaching the drive with different cables and it is not recognized by both BIOS and Disk Management, either the enclosure(in case the drive is an external one) or the HDD itself is damaged.
Your safest bet for recovering the data would be to contact a data recovery company.
Clicking indicates some mechanical error. It could be related to the read/write head or the access arm.
Your only option is to seek for some professional help.
Do not attempt to open up the drive as it could get dust contaminated.
I normally would never write in all-caps, but.... DO NOT OPEN YOUR HD! You need a clean room and professional equipment to open up the HD. There is absolutely no way to recover the information on there without professional assistance. This costs anywhere between $500 and $2500 to start. What you've encountered is a pure mechanical error and cannot be fixed by software, period. The reason you can't open it up yourself is because when a particle lands on the plate, at 7200+ RPM it'll scratch the plate like an MC scratches vinyl.
[edit -- update]
I neglected to mention that the magnets in the HD are extremely powerful and when magnetically connected with an object they can easily pinch you to the point that it cuts off blood circulation. Of course, this requires that the magnet touch something metallic or another magnet to form the bond.