Have you done the hardware tests in the troubleshooting tutorial? Run memtest overnight to stress test it.
Then reset the BIOS to defaults, set SATA controller to AHCI.
Where did you get Windows 7? Did you burn DVD yourself? Try the flash stick installer I provided earlier.
Next wipe the HD using Diskpart Clean Command
from Command Line accessed by pressing Shift + F10 at first screen after booting installer. Then format an NTFS Primary partition marked Active to run Disk Check
from Command Line, and try install again.