IMac 2009 too bad

It's very unlikely you downloaded something or broke everything with one download. Also - with at least 4 things not working well - please protect your pictures, emails just in case it's a hardware failure.

When only one thing is broken - it's often worthwhile to poke, learn, understand what broke and look for a fix of that one issue.

For any group of three or more problems, there's one solution that always works (and often saves a lot of time):

1. Back up anything you can't afford to loose and get someone who is a bit tech savvy to verify you have a workable backup that you can restore if needed.
2. Erase the mac and install just a clean system from the media that came with the mac.

This will quickly let you know if the hardware has failed. It will also solve nearly all software issues. Once you have surfed the web, made sure it is reliable, then you can run updates, restore your personal files and get on knowing it was just some corruption of the software.

Don't feel bad getting help from someone (even paid) if your savvy is for things other than a computer. A good tech can erase and install Mac OS X in 10 to 30 minutes. A good tech might take 4 hours to 4 days to pick apart all the things that could be wrong and tell you what happened. With multiple issues, it's hard to tell what was the root cause and what was just a subsequent failure.

It's often so much easier and efficient to just clean up the mess, start fresh, and keep an eye for any sign of the problems recurring. You will then have better data on the problem. You will also have a backup of your important files.

Since your computer can't tell if it has enough memory to run, (or is truly out of space) you can't really trust itself to fix itself which is why I jumped right to backup / restore for anyone on a situation as you describe. Also, if you were to determine exactly what broke, and did the fixes right, if it freezes or doesn't complete your fix - you will still be in the same badly working situation.

Best of luck - some good people have made answers with great advice here as to what could be wrong. I wanted to weigh in with a different sort of advice since no-one (you included) had mentioned protecting your data files.

As you have seen, all Apple products actually run even when you power them off. On iOS, the battery keeps time and on Macs, the SMC is responsible for knowing when the power button is pressed and if the Mac should start itself up due to a scheduled wake or power on being saved in the NVRAM.

If you called for service, Apple would likely focus on several things:

1. Have you checked that the firmware and software is up to date.
2. Does this happen every single time, or is it an occasional thing.
3. Have you disconnected everything (including the mouse and keyboard) and tested to see if it's in any way related to a peripheral.

Assuming you can reproduce this at will (it happens every time), you would probably take steps to reset the SMC to ensure it's getting proper readings from the temperature sensors.

• Intel-based Macs: Resetting the System Management Controller (SMC)

If after spending the 10 minutes it would take to read through each and every step (I feel it's important to perform the steps in order - even if they seem unrelated or unnecessary), I would expect them to want to run diagnostics to physically open the Mac to check the sensors and wiring. Your symptoms sure sounds like the SMC either is stuck in some loop and not reading the temp sensors. Failure to control the fans properly could also be a hardware issue where the SMC is receiving a signal where the correct action is to keep the fans not only spinning, but spinning at an elevated level.