Macbook pro shuts down on stuartup

Question

I have an older (2008) Macbook Pro, apart from being slow to respond these days it otherwise works fine until yesterday.  When ON button pushed it immediately shuts down.  There is a half-second cd-drive sound like normal startup sequence but then a faint beep and it shuts down.  The screen remains black thru this, no flashes of any kind.
I have tried a couple different batteries and power adapters, same result.  The SRC reset did not help.  Diagnostics (holding D immediately after pushing ON) does not initiate because it shuts down too quickly.  I'd rather not jam the startup disk in the powered-down drive to try starting from CD, but maybe that's the next thing to try?
My time capsule is up to date with backups so I'm not concerned about data loss but I would like to find a way to have it boot up so I can investigate a bit further using standard diagnostics before 'taking it in'.
Does anyone have some thoughts on this issue?

Answer 1

Reinstall Snow Leopard without erasing the drive
1. Repair the Hard Drive and Permissions
Boot from your Snow Leopard Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer.
If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.
2. Reinstall Snow Leopard
If the drive is OK then quit DU and return to the installer.  Proceed with reinstalling OS X.  Note that the Snow Leopard installer will not erase your drive or disturb your files.  After installing a fresh copy of OS X the installer will move your Home folder, third-party applications, support items, and network preferences into the newly installed system.
Download and install Mac OS X 10.6.8 Update Combo v1.1.
If the above doesn't work then you've had a hardware failure and should take it in for repair. This could be a hard drive failure or some other hardware breakdown.