I'm running OSX 10.5.8. Spoke with support via phone and he said that's why the icon for ICloud is not there. He suggested that I get a CD of Mountain Lion from the app store. I went to the store, but didn't find how to order the CD for my system and the online download if for 10.6.8. Plan to call the store contact during hours tomorrow or soon. Not sure why the ICloud was there one minute and gone the next and the support person said it should not have been on this system. Go figure; computer quirks.
You'll actually need to order a snow leopard DVD first. Then you can download mountain lion via the app store. Confirm you meet the requirements: http://www.apple.com/osx/specs
If you dont, you might be able to get lion instead. That's an order over the phone, to get a redemption code.
And make sure you're actually contacting apple: http://support.apple.com/kb/HE57
You'll also want to confirm your 3rd party apps are compatible before an OS upgrade. Of course, you'll also want to backup your data.
Message was edited by: Imp68