Q: My mac book pro wont start up

You may want to run these "standard" fixes if the problem persists.

1) Try a safe boot.

     Shutdown your machine.  Hold down the shift key.  Poweron.  Wait awhile Wait awhile while you harddrive

       is being checked.

    http://support.apple.com/kb/ht1455

2) Run hardware diagnostics.  It's good for a sanity check.

3) Run disk utility

verify & repair your startup drive

To verify & repair you file system on the startup drive, you will need to run disk utility from you installation DVD.

This article  will tell you how to get to disk utility.  Once in a disk utility, you can go and attempt to recover the disk.

http://support.apple.com/kb/TS1417

To repair your startup drive, you will need to run disk utility from your startup DVD.
Mac OS X 10.4: About the utilities available on the Mac OS X 10.4 Install DVD

http://support.apple.com/kb/HT2055

How to run disk utility from your startup DVD.

1. Insert your  startup DVD  into your reader.  Power down your machine.  Hold down to the c key.  Power on your machine.  This will bootup your startup DVD.
2. This will bring you to a panel asking you for your language.  Pick your language.



3. You you come to the Install Mac OS panel.  Do not install.
4. Click on Utilities menu item.  This will give you a pulldown list of utilities.
5. Click on the disk utility.
6. 
7. You are now in disk utility.  Pick your disk.  Click on repair it should be on the lower right of the panel.
8. Once the repair completes successfully, you should update your permissions.

>

a lot more ways to fix your Mac.

http://docs.info.apple.com/article.html?artnum=106214

http://www.thexlab.com/faqs/faqs.html