If you have the OS X install/restore disc for the computer, or the current
retail install disc for whatever OS X version that is running in it, you could
try and start the computer booting from the OS X install DVD.
That would require holding the C key down on startup, with the disc in
the computer's optical drive. If you do not have the correct software on
an original disc, then you have more than the one problem.
Not knowing what of the many keyboard commands one can try on boot
up of the computer, along with several other re-sets, some of which also
require the removal of the battery and other steps, I really don't know
what else to recommend in the area of startup attempts.
There is a chance the boot volume may have a bad directory due to a
corruption of the System software on the hard disk drive; and a fair
chance that something should have been done that was not. Or, that
something should not have been done, and it was.
Not to be too much of a smart ask, but the hour here/now is going on
midnight and I could be watching Craig Ferguson on the tube...!
If you have tried SafeBoot mode, on startup; holding Shift key down
like, forever, and if or when you get a login screen, and have an admin
password for the installed system on the computer, you could then go
and launch Disk Utility, and use its 'repair disk permissions' feature;
then once that runs its course, restart the computer normally + Hope.
But with the gray-screen on startup issue, and no system boot discs,
you probably have a problem beyond the SafeBoot's checks & repairs
on startup; and beyond the on-board Disk Utility's ability to fix anything.
You could probably be able to see how far gone this situation is, if you
can take the computer to someone; to a real Apple Store, where an
appointment can be made to have a Genius check into it to see what
is going on, and go from there. Since there is no real Apple Store in my
state, that feature is something of a myth; like mosquitoes big as birds.
If there is no official, super nice real Apple Store in your driving area,
you may check into those authorized repairers who are Specialists.
But if you have suitable OS X install discs, for a start, that would be helpful.
What else can you say about the computer? Did if you installed software
and the hard disk drive was too full, there is a chance the operating system
may have been compromised by over-crowding the hard disk drive...
If the previous owner had a bunch of stuff on there (another unknown) then
a situation may have existed prior to your ownership, needing attention or
at least resolvable through a completely new installation of everything, over
a wiped and zeroed hard disk drive. The whole route, & reinstall from scratch.
You could try the ideas spread through this older Discussions post, named:
• *Apple - Support - Discussions: "Computer just keeps restarting..."*
http://discussions.apple.com/thread.jspa?threadID=1292631&tstart=74
Some more information would be helpful.
Good luck & happy computing! 🙂
