Reinstalling OS X from scratch

You don't need to do a wipe and reinstall. I ran my last Mac for over 6 years without a clean install.

1. Most of the system files are read-only and don't get altered, so reinstalling them achieves nothing.
2. With a clean install, you plan to wipe the disk, and put back everything, except the bits that were giving you trouble.
3. It's quicker to do it the other way round: just remove the bits that were giving you trouble!

First, make sure you haven't got any software installed that is running in the background, anything patching the OS, etc, etc.
You can usually find these in System Preferences > Users & Groups > Login Items; also the top level /Library subfolders LaunchAgents and LaunchDaemons.
Next, do a Safe Boot. This will clean various caches and run a minimal system. See if things are better now. (You will want to reboot normally shortly after this.)
Next: create a brand new user account and test the problem there. If everything is better in the new user account, then your problem is in your original account. (So no need to reinstall anything!)
Don't be tempted to move everything to the new account: you just need to delete some things in the old one.
You may find that preference files have got corrupt, and so you can try removing .plist files in <user>/Library/Preferences for various related things. You can always replace them if no benefit is found. You may need to log out and in to test the effect.

Lastly, you should get utility software like Onyx. This is very good for troubleshooting when you have a problem. (You do not need to run any of it regularly for maintenance.)
It has a range of utilities, including cache emptying, preference checking, rebuilding of various databases and indexes, which you may want to try.
It is of course very powerful and you should make sure you have a backup before proceeding.

 

At the very least, I would suggest emptying your caches and seeing if that improves things. Corruption in the caches is a likely cause of sluggishness.

OK. You will need to:
1. Wipe the disk.
2. Reinstall the OS.
3. Reinstall any apps that have installers.
4. Restore any other apps from backup, App Store, etc.
5. Restore your user files.
6. Don't restore your User account preferences, as that may be the source of the problem.
7. Recreate your preferences and settings for every app and part of the OS by hand, or manually sort out which preferences to include, testing whether they affect performance.

On Windows, it seems like a clean install the first thing you do when you get a problem. On a Mac, it's the last.

 

Yes, I mean any "application documents" you have created or downloaded.

If you are going to create a "virgin" state, then fair enough. It will still be a significant amount of time to do all that.

But next time you get some sluggishness, don't be tempted to do it again!

I've owned or been responsible for many Macs running OS X over the last ten years and I've never done a clean install for anything except:
1. installing OS X on a new hard drive;
2. rolling out a complete new image of system disk, complete with apps.
3. downgrading after a Snow Leopard update had a massive bug in it.

I've never felt it necessary to "nuke and pave" just for sluggishness or other issue.

 

I don't have an original OS, what do I do?

I also have a late 2007 macbook pro that I got at the dump. The original HD was gone so I bought a new one and installed it and a charger. Today a friend loaned me Snow Leopard and I tried to install it but got this message:

"Snow Leopard requires Mac OS X 10.5 or later to already be on the system"

Well, there is no OS on the system, no backup, nothing. How do I install an OS on a bare system? Do I just need a current OS with an install disk or something? Or do I have to install an earlier OS (which one?) and upgrade to the most current?

Any help is greatly appreciated.

 

Wow, thanks for this advice! I stumbled upon this thread, because I was going to nuke and re-pave. I have been experiencing some serious slow downs, to the point, I'm wondering if I have hardware RAM issues. I'm going to run through these steps. Is there a way to troubleshoot the RAM, and be sure it is good? I don't live close to an Apple store at all.

8Apples

PS - I really had to comment on this thread so I wouldn't lose it. Besides, I think I stumbled on some real quality, qualified advice here, from an experienced user.

 

Actually thanks to the OnyX posted earlier here, I found the issue. As per Apples Support suggestion of running the Disk Utility and verifying my primary HD, it came up clean. No errors. However, I deleted a few old Prefs as per the steps laid out, and finally got to OnyX. Downloading, installing, and running it, it began diagnosing my computer. It said to reboot with Command-R, and to run the disk utility and repair my primary HD. I did so, it indeed fixed errors that had not been reported in Disk Utility when I ran it. Rebooted, and have lots of free RAM now, almost 1GB, compared to the 20MB I had been bouncing into.

Thanks for the suggestions and help, even though I 'hijacked' a thread, it sure fixed my problem! I will keep in mind that link though if I ever think in the future I'm having Hardware issues!

8Apples