Later, in this case, does NOT mean older.
2007 and later means, newer, more recent models THAN 2007.
Your 2006 iMac will NOT install or run OS X 10.8 Mountain Lion, OS X 10.9 Mavericks OR the upcoming OS X 10.10 Yosemite or later.
Your year and model iMac CAN install and run OS X 10.7 Lion.
OS X Lion system requirements
To use Lion, make sure your computer has the following:
- An Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor
- Mac OS X v10.6.6 or later to install via the Mac App Store (v10.6.8 recommended)
- 2 GB of RAM
This is a $20 U.S.D. paid upgrade.
Found here.
http://store.apple.com/us/product/D6106Z/A/os-x-lion
Backup all your current system and all of your important data, first
Before embarking on a major OS upgrade, it would be wise, advisable and very prudent if you backup your current system to an external connected and Mac formatted Flash drive OR externally connected USB, Thunderbolt or FireWire 800, Mac formatted hard drive. Then, use either OS X Time Machine app to backup your entire system to the external drive OR use a data cloning app to make an exact and bootable copy (clone) of your entire Mac's internal hard drive. This step is really needed in case something goes wrong with the install of the new OS or you simply do not like the new OS, you have a very easy to return your Mac to its former working state.
Next,
If you run any older Mac software from the earlier PowerPC Macs, then none of this software will work with the newer OS X versions (10.7 and onward). OS X Snow Leopard had a magical and invisible PowerPC emulation application, called Rosetta, that worked seamlessly in the background that still allowed older PowerPC coded software to still operate in a Intel CPU Mac.
The use of Rosetta ended with OS X Snow Leopard as the Rosetta application was licensed to Apple, from a software company called Transitive, which got bought out, I believe, by IBM and Appe could no longer secure their rights to continue to use Rosetta in later versions of OS X.
So, you would need to check to see if you have software on your Mac that maybe older than, say, 2006 or older.
Also, check for app compatibilty here.
http://roaringapps.com/
Next,
If you have any commercial antivirus installed and/or hard drive cleaning apps installed on your Mac, like MacKeeper, CleanMyMac, TuneUoMyMac, MacCleanse, etc. now would be a good time to completely uninstall this apps by doing a Google search to learn how to properly uninstall these types of apps.
These types of apps will only cause your Mac issues later after the install of the new OS X version and you will have to completely uninstall these types of apps later.
Once you have determined all of this, you should be able to OS X 10.7 by clicking on the Mac App Store icon in the OS X Dock and then login to the Mac App Store using your Apple ID and password and then input the download code for installing OS X 10.7 Lion.
You can then begin the download and installation process of installing OS X 10.7 Lion from the Mac App Store.
