Serial was not declared in scope. Really...

Come on this is just plain nonsense. Since when do I have to declare Serial??
It gives this error when trying to compile the examplesketch named arduinoISP

Then there is something wrong with your environment. What version of the IDE are you using? What Operating System? Have you installed any libraries recently or support for non-Arduino processors?

Yes this compiles for me. I am on the latest Arduino V 1.0.1

Me too. Maybe because I didn't install on the C drive?

That will not matter.
Try installing it again, maybe something went wrong the first time.

cpu_tester:14: error: 'pinMode' was not declared in this scope
cpu_tester:16: error: 'digitalWrite' was not declared in this scope
cpu_tester:18: error: 'delayMicroseconds' was not declared in this scope
cpu_tester.cpp: In function 'void loop()':
cpu_tester:24: error: expected primary-expression before 'int'
cpu_tester:24: error: 'bitRead' was not declared in this scope
cpu_tester:24: error: 'digitalWrite' was not declared in this scope
cpu_tester:25: error: 'val' was not declared in this scope
cpu_tester:30: error: 'delay' was not declared in this scope

Suuureeee... I really have no clue what could have gone wrong :S

keoni29:
cpu_tester:14: error: 'pinMode' was not declared in this scope
cpu_tester:16: error: 'digitalWrite' was not declared in this scope
cpu_tester:18: error: 'delayMicroseconds' was not declared in this scope
cpu_tester.cpp: In function 'void loop()':
cpu_tester:24: error: expected primary-expression before 'int'
cpu_tester:24: error: 'bitRead' was not declared in this scope
cpu_tester:24: error: 'digitalWrite' was not declared in this scope
cpu_tester:25: error: 'val' was not declared in this scope
cpu_tester:30: error: 'delay' was not declared in this scope

Suuureeee... I really have no clue what could have gone wrong :S

Install and run as Administrator if you are on a recent Windows release.