1. Boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu.
If you are preparing an external or a non-startup drive, then open Disk Utility in your Utilities folder.
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on thePartition tab in the DU main window.
3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Securitybutton, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.
Steps 4-6 are optional but should be used on a drive that has never been formatted before, if the format type is not Mac OS Extended, if the partition scheme has been changed, or if a different operating system (not OS X) has been installed on the drive."
How do I wipe my mac it is really slow and i'm getting to the point where i would like to switch back to a windows computer
What crapware did you install that has caused that to happen? Any of the various software that purports to "clean," "optimize," "protect," "speed-up," or "maintain" your Mac will cause the behavior you see.
If you just wipe it clean and then install the same crapware, you will get the same result.
You should really try to isolate the problems before annihilating them. That way, you can avoid running into the same problem shortly down the line.
However, if you'd just prefer to run your Mac like Windows, filling it up with crap, then wiping and reinstalling periodically, please continue.
As I have commented before, in 20 years using Macs I've done this precisely once, in response to a very particular issue. In most cases it's tantamount to demolishing and rebuilding a kitchen when all you need do is replace a bulb in a light fitting.
Best to trouble shoot the issue and fix it rather than this. Start with a full description of the issue, tell is useful information like which mac you have, how much Ram, what OS? When does the problem occur? Does it get worse the longer the machine is running? How much free space on your mac? And so on.