Not sure which instructions you found, but this outline I made works.
Note the part in particular where you cannot just drag the components of the downloaded ML installer to the flash drive.
Yeah, I'm already past that part. I made a bootable DVD and USB flash drive so can reinstall from either one. The problem is when I restart and hold option! I have the option the choose a drive (Mac HD, Recovery Disk and Install OS X) The fact that it even gives me the option to choose 'Install OS X' means that the USB flash has been detected and the Mountain Lion file on it has also been detected. After choosing 'Install OS X', when I install from usb the mac just shows the 'loading' circle and never stops. When I install from the DVD, the DVD drive can't seem to read it. It just freaks out and makes the sound of a DVD drive trying to read a DVD over and over. I end up having to manually restart the mac using the button on the back.
I'm thinking there is either a problem with my mac (which would suck as I've just bought it 2nd hand!) OR it's just too old to allow me to do what I'm trying to do?!
What exact model is your Mac? You can find out by letting it boot to what's on the hard drive now. When you're at the desktop, click on the Apple at the top left while holding down the Option key. The first choice will be System Profiler.
When that opens, the Hardware Overview is the first thing that comes up. Please post the first four entries; Model Name through Processor Speed. You can just copy/paste them here. Do not include any other info, especially any serial numbers.
I decided to do it myself but found that because it's 2008 and he had updated to OS X 10.7.2, I was unable to use my Snow Leopard disk!
You should definitely be able to use Snow Leopard on any 2008 Mac. Assuming that is it's a retail disk, and not a gray disk from another Mac. The gray ones are machine specific and are only for the Mac it shipped with.
Model Name: iMac
Model Identifier: iMac8,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.8 GHz
I do have the SL Retail disk not the grey one. When I tried to reinstall using it I was given a message saying something about how I can't use this version of the OS!? I have 2 of those SL disks and both say the same thing!
Problem with the mac maybe?
Ok! Not entirely sure why but somehow I've been able to install SL. At least, it's recognised the disk and is currently installing right now. The erasure of the HD also worked! All seems good so far. I'm interested to see if I can install ML from the USB stick after I've done this..?!
To be honest, I'm not all that good with mac tech so I may have done something wrong from the very start o this whole process. In fact, I'd say that's likely the case!! All the same, thanks for all the help guys. People like you are handier to get info from than paying to speak to someone at Apple over the phone!
This is your exact model. If you scroll down towards the bottom, you can see it shipped with Leopard, 10.5.2, and is capable of running up to what they have labeled as "Current", with the caveat:
*This system can run the latest version of OS X 10.7 "Lion" including booting in 64-bit mode. However, it does not support "OpenCL."
Your iMac also qualifies to run Mountain Lion, as noted in Apple's requirements pages.
I would guess what's going on is the hard drive's partition map is Apple Partition Map instead of GUID.
1) Backup anything you cannot afford to lose. You will have to repartition and erase the drive.
2) Boot to the Snow Leopard DVD. As soon as you have the option, go to the menu bar and run Disk Utility. Highlight the main drive at the left, making sure to chose the physical drive, per the following example:
You will now have the Partition button active at the right. In order to check/change the partition map, you have to change the partition scheme to something, anything other than where it says "Current". If you want the drive to be one partition, change it to "1 Partition".
The "Options" button below that will now be active. Click that, select the radio button for GUID and click OK. Give the new volume any name you want and make sure the format is Mac OS Extended (Journaled).
3) Once it's done repartitioning the drive, you can quit Disk Utility. You should be able to choose the drive now within Snow Leopard's installation routine and install it onto the drive.
You may be able to do all of these same steps booted to the Mountain Lion flash drive. I'm just not quite sure if ML will install if it can't see a previous qualifying version of OS X on another drive.
Absolute sterling response. Once again, thank you for your help but as mentioned above, I managed to install using SL...! But you are indeed correct about now not being able to install Ml from USB stick. I guess that was a waste of about $20 on the App Store!! Still, nice to have a fresh mac :)
Many many thanks.
but as mentioned above, I managed to install using SL...!
Oh! I read this part is not being to do that.
I was unable to use my Snow Leopard disk!
But then overlooked your next post where it did work. Snow Leopard was the first version of OS X that (mostly) required a GUID partition map. It still did work though with Apple Partition Map on some cases.
If your drive is now GUID, you should be able to install Mountain Lion. Your Mac does support it.