I don't remember where, but I've read that when command-R doesn't work an option boot should (Edit: offer your Recovery Partition as an option), so your grey screen sounds ominous.
The Option boot
will get you to the Recovery HD bootable partition.
A bootable DVD or external drive
might get further along since it is coming in by a different bus than the HD, but , but it does not sound as if this is getting even that far into the boot process before failing.
- Are you getting a boot chime? If not then a visit to the Genius Desk at your nearest Apple Store is almost certainly in your immediate future.
- Is the battery charged? If not try, charging the battery. In some Mac models if there is not enough battery, or backup battery, charge to keep the PRAM values the system will not boot. Since your MacBook Pro does not have a backup (PRAM) battery it relies instead on the charge remaining in the main battery. While I have not encountered this personally, I suppose a complete main battery failure might cause the same problem.
