>>>I'm trying third time, then maybe I"ll try an Archive and Install if it's not too late. Or I'll go back to apple store, see if it really trashed my system. <<<
Ok so the third time failed again with the same message:
"The installer could not validate the contents of the 'essentials' package."
I tried the Archive and Install option with the same results. Remember the DVD disk has successfully been verified 4 times now.
So I run to the Apple store with MBP and they are very helpful in trying to install from one of their disks with various options.... but to no avail, but now they get to see the error message.
The plan now is to boot from the install disk, format a blank HD with GUID formatting. That should let me install Leopard to it in a Full Erase and Install mode. Then I'll copy my disk contents to that drive, erase the MBP system drive and Full Erase and INstall to that, then copy everything back.
What a hassle. If only I knew I would have avoided it like a copy of Windows ME.
Bad RAM is entirely possible. It seems silly to run memtest or replace it though to install OS X though.I know it's about a century since the last post, but in case it helps anyone, I had this exact problem and solved it by replacing the RAM.
Who'd have thought? That would have been waaaay down my list of things to try, if I'd not read the post above regarding RAM.
So, thanks to that poster.