My Macbook won't start up

so one day i shutdown my macbook and when i went to restart it, it will make the startup sound then go to the gray screen with the apple, and a then there is just a thinking circle underneath the apple. And that is as far as it gets. It just stays at this point... I've tried resetting the PRAM and the SMC. neither helped. any ideas what to do? thanks

Boot the MacBook with your original installation DVD, run Disk Utility from the top menu and verify the hard drive. Allow the verify process to repair errors if any. Keep running verify until all errors are corrected.

If Disk Utility refuses to do a verify or can not "see" the hard drive, that might indicate hard drive failure. Post back and we can go from there.

Regards.

ya so i put the dvd in and restarted it and it still does the same thing...

Did you hold down C at startup to boot from the DVD?

THANKS! ADKhikerVW! i did not know that! and i got some activity so i'm just in the middle of working it out!

so everything worked out! Thankyou SOOOOO much all! just another question... why would this of happened to my computer and how can i prevent it from happening again?

k nevermind. it didn't all work. now my itunes doesn't work. it says "you cannot use the application iTunes with this version of Mac OS X" any ideas