This iMac I'm typing on is apparently 2011 running 10.9.5 = Mavericks.
Twice in the last couple of months it has switched itself off. (no power cut). The latest was about a week ago. When I powered it back up (phew!) it said words to the effect of "something wrong with your operating system", which set me on a hunt, and to this forum for suggestions and help.

It seems I could either upgrade to 10.13 = High Sierra, (I don't even know if that's correct....)
or
buy a reconditioned iMac (I really do not need a new computer nor can I afford one).

There's a 21.5" Monterey for £445 on MacFinder whom I have used before, excellent reconditioned Mac seller but the price made me blink; and a 21.5" Monterey for £386 on Mac Store UK, but I've never used them, can't find many reviews of them, and the price difference seems strange.

If it helps, I use this iMac for: web research, emails, numbers spreadsheets, pages letter writing, iTunes and iPhoto. We had to close our business due to my husband's ill health, so my computer demands are relatively light.

Many thanks in advance for all helpful suggestions, as ever.

It is always easy to spend someone else's money, but for a going on 12-year old iMac I would suggest replacement. A sudden power loss seems to indicate something other than "wrong with your operating system". Also, I found the following about 21.5" iMacs:

"… Apple said the 21.5-inch and 27-inch ‌iMac‌ from Late 2013, the Mid 2014 21.5-inch ‌iMac‌, and the Retina 5K 27-inch ‌iMac‌ from late 2014 will be marked as obsolete on November 30, 2022. When marked as an obsolete product, the iMacs will no longer be eligible for any repairs and services."

How about a newer-ish laptop? Also check out Apple's refurbished section in the Apple Store online. They warrant the products as if they are new.

Many thanks Ira. Whenever I occasionally post here, you always reply.

My instinct is that you are right, and I should buy another one while this one is still working (gulp). I'll check out Apple's refurbished section as you recommend.

The next thing I'm going to ask is how to transfer my stuff from this one to the replacement one. I have not done that for years and years.....

Looking at your sign-off or whatever it's called, I've been on Macs since 1986. I clearly remember the first one, a little beige box. Many many iterations have followed since.

I concur with both of Ira's recommendations. Apple factory reconditioned Macs are virtually indistinguishable from new ones. They even come in the same box as new and with the same warranty and AppleCare Plus eligibility. As to the price differential, when you buy a reconditioned Mac, you have to be aware that Build To Order options can easily add fifty to one hundred percent more to the value and price of a given computer and with factory rebuilt, you take what is available with no BTO options. So without detailed specs on the two machines you mentioned, there is the distinct possibiity you are not comparing Apples to Apples rather an Apple to an Apple pie à la mode.

Based on your description of how you use your computer, a less expensive alternative for you to consider would be an iPad Pro. Not only is it less expensive than a Mac, it is lighter, has longer battery life, simpler to use OS, is arguably more secure, supports the apple pencil, and offers cellular as well as Wi-Fi connections. It is what I currently recommend to all my friends with computing needs similar to yours. (My son just sold the MacBook Pro he was using for web site development in favor of a 12" iPad Pro because he lacks the patience for "fooling around" with the details of macOS -- the same reason that convinced me to switch from a PC to the Mac some twenty-eight years ago when I was training Windows support "engineers" for Microsoft. -- and prefers the Apple Pencil for graphics work.

I checked the official Apple refurbished Macs page earlier: very few options and all of them over £1,000.

Further research reveals a vendor called Tech Trade which is in Scotland. Multiple options but the one I have a keen eye on is a Gold Grade Catalina. Gold Grade = indistinguishable from brand new. With keyboard and mouse included, plus 12-month back to base warranty, at £349 it seems a bargain.

People before me have wondered if this is a scam but more people have investigated and it is not. Trust Pilot reviews good too. (Although Trust Pilot not working on this or any other website with this error: Application error: a client-side exception has occurred (see the browser console for more information).

My only reaction is a 650£ cost differential seems too good to be true and both experience and common sense tell me that if something seems too good to be true, IT IS!

Be very very sure that you are comparing Apples and Apples. Look very carefully and closely at the detailed specifications of both machines. Specifically as many of these items you can get...

• the model identifier (for example iMacPro1,1)
• the model number (for example A8162)
• Order Number (for example MQ2Y2LL/A) <this gives the most information>
• failing that information a detailed model description (for example iMac Pro (2017)
• How much memory does it have?
• How much storage does it have?
• What OS version is installed?
• Does it come with a keyboard? What keyboard model?
• Does it come with a mouse or trackpad? What model?

That differential is between a current refurb and a "Gold Grade Catalina. Gold Grade = indistinguishable from brand new (Added: whatever that means)."

The latter must be three or more machine generations older than the former.

First, you've been identifying the Macs you've looked at by the OS version they're running, which is totally fallacious, because any number of different Mac iterations with as many as five or six years between them can run each OS version.

When you look at, e.g., a "21.5" Monterey," you need to know precisely which Mac it is that's running that Monterey.

Back to basics, though, have you done any troubleshooting - such as Repair Disk - before jumping to the conclusion that you MUST buy a new machine? (Sidenote: Any time you see a cryptic message such as "something wrong with your operating system," you should take a screenshot of it so we can see precisely what it says if you post it.)

Many thanks for the replies, here is an update.

While I was having lunch, "it" happened again. I came back to a black screen. But paying more attention this time, the Mac had not switched itself off, the screen had gone black but the fan could just about be heard to still be running.

I held down the power button and switched it off. Then pushed the power button and it started up again, went to log on screen, and powered up perfectly ok. Hmmm. I think it couldn't wake up from sleep? (I have now set the display sleep for a longer interval...)

Before that, I took screen grabs of the two refurbished iMacs which I mentioned, but do not know how to post screen grabs. Meanwhile, the first vendor whom I have used before, the Monterey has gone, but they're advertising a Ventura for the same price. I had a webchat with a technician there who confirmed that the Montereys have been sold and that the Venturas are the same price of £445. I asked him about Numbers and Pages, saying that according to Apple Support they are installed with the OS. He says my spreadsheets and letters etc. will work fine on Ventura. That's a relief.

Since we had to close our business five years ago, I have no website to maintain; I'm not on social media; I only use this computer for internet research, online shopping, internet banking (essential), budgetary management; emails, photo management (I get photos off the camera to here) and relatively simple stuff like that. Oh there is one card game also. I have no need for massive storage space or all the other whizzy things which come with new computers and do not foresee needing them - hence my aversion to throwing a lot of money at this: indeed £445 seems a lot now that we're retired!

Hope that helps and please reply with any ideas wrt paragraphs two and three. Thanks!

Really pay attention to joemikeb's post above where he suggests the information you should pay attention to, like model, serial number, etc. Let us all know the specs of what you would consider.

I have a "gold grade Catalina" 27" iMac (it could run Big Sur) and it is over 8 years old; it is indistinguishable from a new 2014 27" 4K Retina iMac, but I would not recommend buying it, even with a one year warranty. I will replace it within the next 6 months, if all goes well.

Here is a go at a screen shot. Here

Your screen shot worked.

Can Ventura even run on an Intel processor?

I would say yes. My 2017 (Retina 5K, iMac 27") with the 3.4 GHz Quad-Core Intel Core i5 Processor is able to. I am not using Ventura but, when I checked System Preferences "Software Update" it wants to install Ventura.

Suspicions confirmed! According to MacTracker the iMac in the ad is the oldest version that can run Ventura. Given the Kaby Lake dual core i5 processor, 8GB of memory and 266GB of storage I would anticipate the performance being somewhere between dreary and dreadful. The odds are against its being capable of this year's macOS upgrade and it may already be on Apple's antiquated list, meaning Apple only supports it on a parts available basis and it is a year or two from going on the obsolete list meaning Apple won't touch it. To paraphrase a song from my youth, ...this old mac ia s gettin' ready to meet the saints.

In my opinion, if you are willing to purchase it with the possibility that it may not tolerate the next OS upgrade or the next round of software upgrades and updates or may have to be replaced soon, it might be adequate -- just adequate -- to your needs. I have written and re-iterated the adage that if something seem too good to be true it is, this price may good, but remember you get what you pay for, headaches included.

That particular iMac had a long production run: 6-2017 to 10-2021, so it's still "Supported," and will be for, I believe, another 3 1/2 years.

Rosemary Clooney! (She recorded version with which I'm familiar, anyhow.) I've always liked that song, and despite the fact that I haven't heard it since the '50s, I still find myself singing it from time to time.

Two days ago I emailed Sales at one of these vendors and they have not replied. If people can't monitor sales enquiries via an email address which they have provided, then I'm not doing business with them.

Having spent hours checking Ventura's specifications in multiple respects, I feel that it isn't for me (right now, at least). I also don't understand how it could be loaded onto a machine with 8GB RAM when it says here Link from Google otherwise.

So I'm going to go for a Monterey, partly because it supports (or contains) iWork.

Having said all that, this Mac is behaving itself now. Changing the sleep timing seems to have done it. Shhhhhh!

You're confusing apples and oranges.

Your link refers to disk, i.e., HDD/SSD space, not RAM.

In addition to artie's comment above, Ventura supports iWork in the form of Pages, Numbers and Keynote. Unless you literally mean the single application on a CD that was discontinued in 2012, iWork is alive and well in all Mac operating systems.

Nope, it's Google (confusing the issue). If you have another look at my question, "How much memory does Ventura require?" it replied with disk space.

As I had already pointed out, Google did, indeed, return an incorrect answer, but your question "flew" with it and conflated RAM and disk space.