My iMac is broken

You made it sound quite straightforward, I'm impressed.  Hope all is confirmed to be in order Mr D and a celebratory tipple can be had instead of copious amounts of coffee.

Am typing this from the iMac, having restored my MBP's clone onto it.  But...hmmm.  Trying to do a restore from the Time Machine backup I did before the original HDD finally went kaput, and it doesn't want to play...

Wait till you see the how-to post (with pictures)...

Ah, well there's nothing straightforward about that

Finally.  Have found my Snow Leopard install DVD, which is apparently required to do a full restore from a Time Machine backup (more on that later)...

6 Hours and 26 Minutes? Sweet Jesus!

It was more like three to be fair. But I hate leaving things like that running overnight only to wake in the morning and find it's failed or gone to sleep or whatever, so I blogged it up...

www.whathifi.com/blog/replace-the-hard-drive-in-your-imac

Just found this article John...

http://www.theregister.co.uk/2011/05/14/imac_hard_drive_replacement_woes/

...is everything ok on yours post replacement?

Time Machine can be used for on-demand backups; simply right click the dock icon and choose 'back up now'. There is no need to keep the disk attached.

It's fine, yes.  When I enquired with a service centre about them doing the work, he did ask model number so that he could identify whether it was a normal hard drive or whether it needed "a specific apple one with temperature control built in" and was told it was just a normal one, which seems to be the case since mine had the stick-on temp sensor and is showing no ill effects.

Finally got round to putting a new hard drive in - delayed by 'flu.  Much easier than taking the iMac to bits - took less than an hour to put together again.  Started perfectly!  I have installed LinuxMint rather than apple software - again went very smoothly.

(This was my wife's iMac.  It was over six years old when it died, so rather than have it 'officially' repaired she bought herself a new one: bigger screen, bigger hard disc, four times the memory, Lion software etc.  I got the broken one to play with.  I also have her old mobile phone and her old her old iPod nano.  Well, I am old, 70 in just over 3 hours.)

Apple certainly does not make it easy to repair their stuff, but it is possible with patience, a lot of bad language, and an occasional extra hand.

Andrew

Enjoy your birthday- and look forward to the next 70 by 3.00am.

For backup software consider Crashplan.  It's free and as well as backing up to an external HDD you can backup remotely to a friends computer.

I've given up relying on single external HDDs for backup having had too many fail on me.  I now use a Drobo, which has capacity for 4 x 2TB HDDs.  Everything is mirrored so a disc failure is no problem and it's TimeMachine and Crashplan compatible.  If I were buying again I would get the 5 bay NAS version.