Wd800jd Internal Hd(sata) Boot-up Issue.

Your hard drive is bad.  It needs to be replaced. You have a couple options to recover the data: Buy a new SATA drive, load your operating system on it.  If your PC has another open SATA port, connect your bad drive to it. Your bad drive will appear in My Computer as the E drive or F drive most likely. You can then copy over the data from your bad drive to your new drive (C:)

If your PC does not have an open sata port, you can buy a SATA hard drive enclosure.  I recommend this one: http://www.bestbuy.com/site/Rocketfish%26%23153%3B+-+USB+2.0/eSATA+Hard+Drive+Enclosure+Kit+for+2.5%22+SATA+Hard+Drives/8774301.p?id=1204332553274&skuId=8774301&st=SATA%20hard%20drive%20enclosure&cp=1&lp=3

You would place the bad SATA drive in the enclosure and hook up the enclosure via USB to your PC.  The bad drive will appear as another hard drive in My Computer, as the E or F drive.  You can then copy the data over to your new drive (C:).  This option will work if you want to copy over to any PC (another PC you have, a friend's PC, etc) to recover that data.