verify the SHA1 hash on the windows disk to make sure its not corrupted. I've had disks that seemed to be in perfect working order, boot up to install, no hard drive, verify the USB installer and get hash-fails. remake the installation USB from a working master, and boo-ya! hard disks found.
The fact that the install took seven hours is a good sign either the disk is bad, or the hard disk / hard disk controller has a problem.
Check the drive to ensure it is tightly secure.
Try resetting the BIOS to factory defaults.
Try changing HDD modes in the BIOS. try out IDE, AHCI and RAID to see if any help.
Try running a S.M.A.R.T. check on the drive and check the S.M.A.R.T. logs.
Try the drive in a different computer.
Here is a lil more info on S.M.A.R.T. status codes:
http://en.wikipedia.org/wiki/S.M.A.R.T.#Known_ATA_S.M.A.R.T._attributes
For Seagate, Samsung, Maxtor, Hitachi and Toshiba hard drives:
http://www.seagate.com/support/downloads/item/seatools-dos-master/
For Western Digital, / WD drives:
http://support.wdc.com/product/download.asp?groupid=613
For all others:
http://www.almico.com/sfdownload.php