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Please read the warranty paperwork that came w/your computer.
You have 14 days to return the computer w/no questions asked.
You have 90 days of FREE phone tech support on top of your standard 1 year warranty unless you also purchased AppleCare which gives you an additional 2 years of coverage plus FREE phone support.
Strongly suggest that you take FULL advantage of the above before it runs out. Let Apple deal w/the problems.
Where is there a sequential set of training, like on a PC, to learn OS X?
The OS Help Menu.
Apple’s troubleshooting website: Mac 101
The following reference book: OS X Mountain Lion: The Missing Manual - David Pogue . This book is very easy reading, non technichal & non geeky. I strongly recommend this book as it takes you step-by-step through Mountain Lion.
Strange that you have a ML on a recently purchased Mac. All new Macs come pre-installed w/Maverick. Where/Who did you purchase your Mac from?
Are you selecting your user account and navigating to the various folders in it. Without doing that, nothing is diplayed by Finder.
Welcome to the world of Mac. Some ‘light’ reading to help the transition. I don’t recommend trying to get through all of this at once.