If you have a second hard drive with a working partition not necessarily any OS but the same type of partition, Fat, NTFS, etc. you can use a free live OS for the cost of a cd-r to gain access until the drive is restored. That would be a live for cd Linux distro like ubuntu. The image here shows how files are being copied from a usb external drive to an internal sata model while booted from a live cd.
If you are running XP the recovery console can be used for seeing the boot information rewritten at no charge with two simple commands. Or if you have a full install disk for XP a repair install of XP could make that happen as well since that will replace any corrupted boot files.
For Vista the full install disk now sees an automatic startup repair tool that will repair most problems when booting from that to select the repair tools not install now option. All this will depend on a working drive however. If the read/write heads failed then a pro service for a high price would be needed! ouch alright!