Check if another PC can "see" this drive in Disk Manager (or Disk Management), under Administrative tools in Control panel. If it does, you can try to initialize the drive again (if it asks you to, but you will probably lose all the data on it). If not, see if it can be mounted under a Linux OS PC (that will probably fail, too, but worth a try). If still no dice, and data very important, you might have to send it to a data retrieval firm. They actually take it apart and replace the controller on it, or even take out the platters and get the data off of them. That's pretty expensive, though.
If data not that important, you can download Killdisk and run a wipe on this HDD mounted as an external HDD. That is, if the HDD is seen by this program. Download and burn a bootable CD with killdisk on it, install the HDD as a single drive on your PC (any other HDD disconnected), boot from CD and see if it can detect the HDD. From there, follow the instructions and do a complete zeroing of the drive. Then use any program of your choice to re-format it. Keep in mind, you WILL lose all the data on it, but you get the HDD back (at least for a while, you don't want to keep important data on it anymore, it may be failing again soon).