Start by checking if you can run Snow Leopard:
Requirements for OS X 10.6 'Snow Leopard'
The OS 10.6 Snow Leopard install DVD is available for $19.99 from the Apple Store:
and in the UK:
When you have installed it, run Software Update to download and install the latest updates for Snow Leopard to bring it up to 10.6.8, or download the combo update from here:
Check via Software Update whether any further updates are required, particularly to iTunes.
You should now see the App Store icon in iTunes, and you now need to set up your account:
You can now upgrade to Mavericks OS 10.9 for free IF you have one of the following Macs, with not less than 2GB of RAM, and at least 8GB of available space on your hard drive:
iMac (Mid-2007 or later)
MacBook (13-inch Aluminum, Late 2008), (13-inch, Early 2009 or later)
MacBook Pro (13-inch, Mid-2009 or later), (15-inch, Mid/Late 2007 or later), (17-inch, Late 2007 or later)
MacBook Air (Late 2008 or later)
Mac Mini (Early 2009 or later)
Mac Pro (Early 2008 or later)
Xserve (Early 2009)
If you cannot run Mavericks you can purchase the code to use to download Lion from the App Store (Lion requires an Intel-based Mac with a Core 2 Duo, i3, i5, i7 or Xeon processor and 2GB of RAM, running the latest version of Snow Leopard):
or Mountain Lion:
I ran into this problem too. After inheriting this imac from my mother, I found out it is pretty much only good for the basics--essentially, you can't download much because the OSx that is originally installed is "useless". In other words, it's totally and utterly outdated!
Eventually, you won't be able to upload anything at all, since the osx will be unusable.
Furthermore, the "newest" Osx that this imac will download is Snow Leopard, since it is the last one offered on a disc
You cannot upload an update, since this imac runs on disks (that tells you how "old" the computer is). You HAVE to order the disc from Apple. I called support, and they sent it for free. DON'T PAY FOR IT!!!!!!
FYI, I was also told not to even think about bringing this computer into an apple store if it breaks. She said they will essentiallly laugh you out of the store. They don't even have the parts to fix our machines. So treat your imac gingerly.....it's regarded as an "antique"!!!!!!!
Ok, so your comment is basically 100% incorrect. Not ripping on you, just trying to help out.
First, if you want to upgrade to newer OSX's and your iMac can handle them, you can, just because they don't come on a disc doesn't mean you can't use them. If you get the Snow Leopard disc(20 dollars) from Apple, your iMac will upgrade just fine. Then if you simply go the apple symbol in the top left corner, click it, select "about this mac" from the drop down, you'll see something about checking for updates. Click this, install the updates and you'll have your Snow Leopard updated to the newest version of OS X 10.6. At this point you'll see a new app called the App Store in your applications folder. Open it, search for Mountain Lion. By a simple single click. for 20 dollars you'll be upgraded from Snow Leopard to Mountain Lion. That will be the last dollar you'll ever have to spend for an upgrade. Every one after that(Mavericks, Yosemite) are 100% free. Now, you might not want to upgrade all the way to Yosemite, just like an older PC windows computer either can't, or shouldn't be upgraded to windows 7 or 8. But your iMac certainly can upgrade to snow leopard if it has an Intel processor and at least 1 gb of ram. From there you can do some research and see if you're iMac can handle moving up to Mountain Lion, if it was released in 2007 or after, I assure you it absolutely can. But even if it can't you can still run a plethora of good programs on your older iMac running Snow Leopard, which brings me to my next point.
When you go to look at using new software, and you're using an older version of OS X like Snow Leopard, you just have to download the older version that matches your operating system. Do this by googling '"name of software" Snow Leopard compatible version'. It's too bad that computers that are bought 8-10 years ago can't run the newest versions of software, but the fact is it's physically and technically impossible for it to do so. Advancements happen, and holding back advancements only hinders productivity and choice. Like someone noted above, many people choose to stay at Snow Leopard, because you can run Intel based programs, AND powerPC based programs. If you follow the steps I've given you, you'll get plenty out of the iMac your mother gave you. But if you're looking to use the most cutting edge and advanced software versions out there, you'll need a little better machine. But not that much better. My parents have a 2007 iMac, and it runs the current OS X 10.10.2 just fine. Hope you find a way to get more joy out of the machine your mother provided you with. Cheers.