You could try with Diamon Edge, the best disk tool pack on the scene. It has helped me out several times in situations like yours.
D/E has functions like repair/autofix errors/diagnostics/defrag/undelete and much more. With it comes also DADE, a superduper disk-&-sector-editor with an advanced cluster/sector-calculator, and functions for tracing of fragments!! IF nothing can fix your bootsector (and I reckon that's it) and the FATs still are OK, then DADE can hunt your files up, one by one... A very time-consuming job, I have done it on a couple of (small) HD's, but at least I got my files back.