iMac really slow - want to do a fresh install

Discussion in 'iMac' started by snowmaan, Dec 9, 2012.

  1. macrumors regular

    Sep 29, 2008
    Sydney Australia
    It's so slow and hangs constantly when opening even small files or programs. It's around 3 years old now so it's had a lot of work and junk installed over the years I guess

    What's the best way to do a fresh install nowadays?

    I don't have the original disc but I have the disc from when I upgraded to Mountain Leopard recently

    Also any tips on doing it, things to avoid, good ways to backup data etc

    I have an external HDD and also regular time machine backups

  2. macrumors member

    Oct 28, 2007
    Before doing a fresh installation, doing an authorization fix and disk check may help.

    You need to boot up from your installation disk (or USB), run disk utility from there and check/fix authorization on your bootdrive. Also do a check disk / fix boot drive using disk utility.

    If it's still very slow, check the SMART status of your drive. It might be time to replace the drive.

    My iMac went dead slow with drive problem, twice.
  3. macrumors 603


    The problem here is Mountain Lion, seems to be slow with many users.
  4. macrumors 68030


    May 20, 2010
    Los Angeles, CA
    You have two options.

    1. Reboot holding down Command-R; this will boot you into the Mountain Lion recovery partition. Use disk utility to wipe/reformat your system volume/partition, and then you can reinstall Mountain Lion afresh. It'll prompt you for your AppleID to verify that you own Mountain Lion, and then once that check passes, your computer will download and install the OS on the spot. Get cozy, it'll be a while. When it finishes, you'll be ready for takeoff.

    2. Go to the App Store, redownload Mountain Lion. Quit the installer app when it loads upon the completion of the download. Find the installer in your Applications folder. Right-click on it, and go to Show Contents. Then navigate to Shared Support. You should see a file in there called InstallESD.dmg. Copy that file elsewhere so you're not using the version in the app. Then from the newly created copy, right-click, and select open with, and then Disk Utility. Or just drag that file into Disk Utility. Or open Disk Utility and navigate to the newly copied InstallESD.dmg file. Either way, you get the idea. From Disk Utility, either:

    A. burn InstallESD to a dual-layer DVD or:

    B. take a thumb drive, no smaller than 8GB, and format it as Mac OS Extended (Journaled), and under Options, make sure it uses GUID and not Apple Partition Map or Master Boot Record. Once your drive is formatted and ready to roll, go under the Restore tab and under Source select the InstallESD image, and under the destination, select your thumb drive. If that fails, try mounting InstallESD.dmg and under Source, selecting Mac OS X Install ESD (as that sometimes is necessary).

    Either way, this will leave you with a perfectly bootable 10.8.2 install media.
  5. macrumors member

    Aug 5, 2012
    Los Angeles - California
    Be also sure you didn't put much thing on your desktop, its gonna slow down your computer!
  6. thread starter macrumors regular

    Sep 29, 2008
    Sydney Australia
    That's great, thanks very much all

    Yebubbleman - option 1 seems blindingly better / easier than option 2?

    I will definitely try an authorization fix and disk check first I think. I reckon the HDD is not in great shape, as I think I ran a check on it before, and whilst it seemed to pass ok, it has plenty of capacity left, so it should be a loaded drive issue I think

    It was really slow before Mountain Lion unfortunately
  7. macrumors 603


    Option 1 is faster if your internet connection is reasonably fast.

    And yes it is always smart to check the disk first, you do NOT have to do this from another bootable disk, you can check the disk if it is OK, if not then you have to run it from another bootable disk or recovery and repair there.
    Repairing permissions CAN be done in your System, you don't need to run this from another disk.
  8. thread starter macrumors regular

    Sep 29, 2008
    Sydney Australia
    Excellent, thanks justperry
    I will go and work out the best way to check the disc then and give it a shot

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