I have a macbook pro and am running OS X snow leoplard 10.6.8 and my macbook will not start

To clarify my Macbook will make its normal chime that it makes when it turns on. The fan will start and the sceen turns on but freezes with the apple logo and the loading going. I have tried every diognostic test I could find.

Powered on holding shift to power on in safe mode

It gives me a loading bar which appears under the loading gear but it disapears after about 30 seconds before it finishes and the laptop goes back to just being the apple logo and the spinning gear

I powered on holding down D and ran an extensive hardware test, the results of which came back fine.

I powered on holding T and C to no avail

Finaly i tried single user, I first tried renaming my library incase that was the problem but after making sure that was corrected the problem persisted

So i read this article and used the /sbin/fsck -fy command

after checking through the first few entries the line reads

** Checking volume bitmap

Volume bitmap needs minor repair for under-allocation

** Checking volume information

volume header needs minor repair

(4,0)

** Repairing volume

disk0s2: I/O error.

disk0s2: I/O error.

disk0s2: I/O error.

disk0s2: I/O error.

disk0s2: I/O error.

disk0s2: I/O error.

** Rechecking volume

** Checking Journaled HFS Plus volume

Invalid extent entry

(6, 487725342)

** The volume Machintosh HD could not be verified completly.

disk0s2: I/O error.

I have run this three times and all three have resulted in the same outcome. I can not find anything about what "disk0s2: I/O error" actually means and I am not sure how to trouble shoot any farther. If you have any suggestions I am all ears.

(worth noting the other checks such as "extents overflow file", "catalog file", ect all take a considerable amout of time but the error messages that I listed out ring up almost instantaniously)