Hi,
One is looking in the wrong place.
There are three folders called "Library"
The one in Hard Drive > Library
The one in Hard Drive > System > Library
And the Hidden one if you are using Lion in Hard Driver > Users > (Your account/Little House iCon) > Library.
This Hidden one can be seen if you use the Finder > Go Menu and then Hold the ALT key to see the Library get added to the list.
Then you can open Preferences.
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iChat can send Messages (IMs or Instant Messages) to valid AIM Names or to Jabber IDs
It cannot send iMessages like Messages Beta can or the iPod Touch can with the iOS 5 messages app.
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The OS can be reinstalled several ways.
One is to use the Lion restore option which mean starting the computer holding down the CMD and R at Start up then choosing the "Recovery" Drive.
http://support.apple.com/kb/HT4718
There is a USB Memory stick drive that can be purchased and I would not be surprised if the Stores made use of this.
I would also think that Apple may provide the Stores with DVDs that can install the OS.
I was hoping that you either saw the process or the Chap told you which method was being used.
7:48 PM Tuesday; July 10, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously