patching a crashed hard drive

[Roy W. Erickson]

All:

My computer fell over hitting the floor with a pretty good thud, while 
up and running. The screen froze along with the mouse and keyboard.

It broke the CD-RW, but the machine booted anyway. I was very suspicious 
about its integrity so I ran this:

dd if=/dev/hda of=/dev/null conv=noerror

Sure enough I get "Input/Output errors" on certain segments of the HD

What can I do to try to patch over these segments?

Thanks,

Roy