Where did you get Windows 7? Did you burn the ISO to DVD yourself? If so, confirm ISO or download another, burn to DVD using ImgBurn at 4x speed.
Next try writing ISO flash stick using
Universal USB Installer with Windows 7 in the dropdown menu.
Test your HD using
Seagate SeaTools extended CD scan, which can also wipe the HD afterwards before trying install again.
Next try install after removing all but 2gb of RAM. Then swap RAM sticks. TEst your RAM:
RAM - Test with Memtest86+ CD for 5-6 passes or overnight.
Unplug all other HD's and peripherals. REset BIOS to optimal defaults in BIOS Setup. Report back all results.