If your is not a SSD and If there is a phisical error on disk, like a depression or surge, you can reformat it, but each time the disk header goes over the wrong area, it expands the problem.
Usually, if W7 was preinstalled, you should have a partition with the 'reinstallation' and 'diagnostics'.
Usually, after the preinstallation has finished, you created a DVD or some thing alike, with all this stuff.
With the diagnostics, there should be one that can verify your disk for hard errors. Also you can fully test your memory and video cards.
If this is the case, the only solution is to replace the disk.
Oh, I assumed that after all the trys, you also tryed to start in safe mode without networking and, even in this situation, you are not able to load the OS.
Also assumend that, after all the boot interruptions, a chec disk was performed.
Well, hope this helps