MBP Won't Boot

Resetting your Mac's PRAM and NVRAM

Intel-based Macs: Resetting the System Management Controller (SMC)

Restart the computer in Safe Mode, then restart again, normally. If this doesn't help, then:

Reinstalling Mavericks, Lion/Mountain Lion Without Erasing the Drive

Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.

When the recovery menu appears select Disk Utility. 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 main menu.

Reinstall Lion/Mountain Lion, Mavericks: Select Reinstall Lion/Mountain Lion, Mavericks and click on the Continue button.

Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.

Swollen battery? Keyboard not attached to the logic board anymore (flimsy connection in best case scenarios)? Looks like your keyboard isn't operable, and that could explain why you can't boot, because your MacBook Pro needs an input peripheral of some kind. Also, remember that the connection between keyboard and logic board caters to the trackpad too.

Since you've got a Unibody Mac, you probably should take it to the nearest Apple Store or Apple retailer to have it checked against what I've just described. I could be wrong, of course. I've been known to be wrong once or twice... 😁