iMac and spinning beachball of death

Hello, I'm looking for some help with my wife's iMac. We bought the machine in 2008 and, in general, it hasn't caused any trouble for the entire time we've owned it. However, recently its started running extremely slow and displaying the SBBOD with great frequency. Rebooting does not help/

I'm a career software developer who is quite adept with software and hardware diagnostics but the vast majority of my experience is with Windows so I'm a little in the dark here. I've done the following:

- Used activity monitor to check memory and CPU utilization. Nothing unusual, plenty of free memory and no processes hogging CPU
- Checked disk free space, plenty of disk available.
- Quit all apps, Finder still shows SBBOD when navigating the Finder itself
- Reset the SMC, no real change
- Uninstalled various bits of unneeded software
- Ran hardware diagnostics, no errors
- Looks at various posts about SBBOD, tried various remedies to no avail

Nothing has really helped.

This machine has had a tough life for a while with my wife, daughter and her friends installing god knows what on it over the years. I've made various attempts to keep it clean but I really only pay attention to it when it misbehaves and that has not been often and never severe.

In my Windows experience this is the time you would decide to back off all essential data, wipe the machine and re-install from scratch. I'm completely confident in my ability to do that but I hate to do it unless its the right answer. Given that I've gone through as many of the various SBBOD remedies and none of them panned out, I'm fresh out of ideas.

Any help?

Two things:

- How much ram does this computer have?
- The main problem could be a dying hard drive.

* Nick

How much free space? If over 25-30%, even though the drive is very likely highly fragmented, it's "probably" a drive on it's last legs.

I would back up the drive "now", before doing anything else.

Not necessarily in the following order - If you've removed all 3rd party items that start up at log in, run Verify/Repair Disk (what sort of errors/repairs were made if any?), reset both PRAM and SMC, you don't have an anti-virus, parental control software or some 3rd party "cleaning" software installed, and you're getting minute plus long beach balls with native apps - I wouldn't think twice about ordering a new drive if it was my own machine. Personally, I'm still recommending the WD Black for those not wanting to spend the cash on an SSD for older machines.

Thanks for the replies.

I believe the machine has 2Gb of memory could be 4 though (it was a top-end iMac in 2007). Since it only recently started having problems and nothing major has been installed on the machine recently I pretty much discounted memory issues. Also, under activity monitor there is still plenty of memory free.

- All login items have been removed
- I've run verify disk and it ran clean
- Haven't reset the PRAM so, I'll try that
- No anti-virus that I'm aware of but I'll re-check

Disabling login items was easy but I'm not certain that's all that starts when the machine boots. Perhaps there are other processes that are starting at boot that are not listed as account login items? I would think they would show up as active in Activity Monitor though.