I found this OLD late 2010 MBP that came with Lion. The computer works fine and is not locked. There are a few issues though. When I try to do an internet OS restore, it'll just say downloading files and then give me an error, so that's not an option. I did one get it to do a full OS reinstall, but I am not sure if it was because the installer miraculously worked, or it was a DMG iso I burned to a flash drive with TransMac. Because trying to use that same flash drive again won't let me do a clean install. However when I did get lucky that one time and got a full Lion re-install, I come to find out that I CAN'T update to High Sierra or any other OS unless I first get Mountain Lion. But you have to PAY $20 to get Mountain Lion. So I tried doing the same with a Mountain Lion DMG to USB and got stuck. Their disk utility is so much more confusing than Windows. With Windows you just delete all partitions and click next and the OS will get installed. Macs are completely different and complication, and I thought they would be easier. Anybody have an idea on how to successfully burn a DMG to a flash drive either on Windows or Mac disk utlity, and get High Sierra successfully installed, without having to pay Apple $20?
To create a bootable USB stick from a recent OS install dmg for Macs, you need to use the "createinstallmedia" command that comes inside the dmg. The dmg itself cannot be written to a USB stick and used to install. Detailed steps for the various versions. I can't post links yet, so go here: support.apple.com/en-us/HT201372 For Mountain Lion, and earlier you need to follow a different process. At a high level, you format your thumb drive to the correct boot partition type (Mac GUID, which is of course, slightly different than other GUID boot partitions). Then you'll use Disk Utility to "restore" a DMG that is inside the Mountain Lion installer app to the thumb drive. (All OS, including Windows, have a separate, tiny, boot partition. But in the past it was just called a "boot record" because that's all it contained. GUID boot partitions/records are much bigger and can contain a load of other stuff.) Step by step: Format a 5gb or larger USB thumb drive as a GUID partition. Open DiskUtility and click on the flash drive in the left side panel, not the partition. On the right panel, select a single partition and make it Mac OS Extended (journaled), which should be the default. Click the partition, then click the Options button. In the pop-up, select GUID Partition Table and click OK. Click Apply back in the first window and it will format the thumb drive. Find the Mountain Lion Installer app and right-click on it and choose Show Package Contents. This will open up a Finder window that shows you what is inside the app. Drill down into the Contents folder, and into Shared Support. Inside Shared Support there will be a disk image named InstallESD.dmg. Launch Disk Utility Drag the InstallESD.dmg into the left side panel of Disk Utility below the other disks and volumes that show up there In the left side panel, click to select the InstallESD.dmg, then click the Open button in the toolbar to mount the DMG's volumes in the Finder. You'll see a mounted volume show up in Finder called "Mac OS X Install ESD". This will also show up in the left side panel of Disk Utility, below the InstallESD.dmg. Select Mac OS X Install ESD in the left side panel, then click the Restore button near the top of the right panel (First Aid | Erase | Restore). Mac OS X Install ESD should show up in the Source field for the restore, if it doesn't click and drag it from the left panel into the Source field bar. Plug in your thumb drive if you haven't already. Once it shows up in Disk Utility's left side panel, drag the partition (not the disk) you created in step one into the Destination field bar. Click Restore. In the warning box that pops up, click Erase. You may get prompted for your password, if so enter that to continue. Depending on the speed of the flash drive, it will take 5-10 minutes to do the restore. If you want to install versions of MacOS onto your laptop that are not supported on it, I recommend looking into OpenCore, since it allows you to install unpatched, vanilla versions of MacOS: dortania.github.io/getting-started/ OpenCore is more focussed on the Hackintosh community--installing Mac OS on non-Apple hardware--but it also works for installing newer Mac OS on older, unsupported Macs.