Q: spinning wheel, hardware test? if apple was designed properly (with the use in mind) surely these error would not occur? and shouldn't the system self diagose and let you know the problem.  ie the left front tire is flat, fix it ...

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If you have a question, ask it, if you have a problem, describe it.

It would help us to know which iMac model you have, how much RAM, etc. You can have this info displayed on the bottom of every post by completing your system profile and filling in the information asked for.

This will help in providing you with the proper and/or correct solutions.

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Please detail ALL you have done so far in the way of troubleshooting?   Need this info to avoid the been there done that scenarios.

How large is you HD and how much space do you have left?

Also, check out KB Article
http://support.apple.com/kb/PH11342 OS X Mountain Lion: Use Apple Hardware Test since that was one of your questions.

Also, How full is your Mac's hard drive?

How many applications do you run simultaneously in the background while working in another application?

Do you run any antivirus software on your Mac? Antivirus software can slow down the normal operation of OS X.

Do you run any "crapware" like Mackeeper or any other type of so called hard drive "cleaning" apps?

First, back up all data immediately, as your boot drive might be failing.

There are a few other possible causes of generalized slow performance that you can rule out easily.

• Reset the System Management Controller.
• If you have many image or video files on the Desktop with preview icons, move them to another folder.
• If applicable, uncheck all boxes in the iCloud preference pane.
• Disconnect all non-essential wired peripherals and remove aftermarket expansion cards, if any.
• Check your keychains in Keychain Access for excessively duplicated items.
• Boot into Recovery mode, launch Disk Utility, and run Repair Disk.

Otherwise, take the steps below when you notice the problem.

Step 1

Launch the Activity Monitor application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Activity Monitor in the icon grid.

Select the CPU tab of the Activity Monitor window.

Select All Processes from the menu in the toolbar, if not already selected.

Click the heading of the % CPU column in the process table to sort the entries by CPU usage. You may have to click it twice to get the highest value at the top. What is it, and what is the process? Also post the values for % User, % System, and % Idle at the bottom of the window.

Select the System Memory tab. What values are shown in the bottom part of the window for Page outs and Swap used?

Next, select the Disk Activity tab. Post the approximate values shown for Reads in/sec and Writes out/sec (not Reads in and Writes out.)

Step 2

If you have more than one user account, you must be logged in as an administrator to carry out this step.

Launch the Console application in the same way you launched Activity Monitor. Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left. If you don't see that menu, select

View ▹ Show Log List

from the menu bar.

Select the 50 or so most recent entries in the log. Copy them to the Clipboard (command-C). Paste into a reply to this message (command-V). You're looking for entries at the end of the log, not at the beginning.

When posting a log extract, be selective. Don't post more than is requested.

Please do not indiscriminately dump thousands of lines from the log into this discussion.

Important: Some personal information, such as your name, may appear in the log. Anonymize before posting. That should be easy to do if your extract is not too long.