Have you ruled out the possibility that only your boot loader is broken? With the Windows installer CD, there's an option to repair your existing installation if it finds that the bootloader is still repairable.

Though given the way you use your laptop and its sheer age, it's also very possible that the drive is simply just dying. Best to take it out and save all your files before the entire drive conks out. Then you can decide what to do from there - you can reformat, you can try to have it repaired, you can get a new hard drive (a 2.5" 1 TB hard drive would set you back roughly 4k), you can upgrade to an SSD (180 GB SSDs are now only 6.5k), or you can get a new laptop altogether.