... I already clicked on the Apple symbol on the top left part of my screen and clicked "Software Update'' but it says I am up to date, which clearly is not right)
It is Correct for your Current OS = Leopard = 10.5.8
The first step in Upgrading... is to Snow Leopard = OS X 10.6.x
It is Not available as a download...
Do this first...
Check that your Mac meets the System Requirements for Snow Leopard...
Snow Leopard Tech Specs
If so Contact Apple in your Country to Purchase a Snow Leopard Disc...
In the US...
1-800-MY-APPLE or 1-800-676-2775
After the Successful Install, run Software Update to get the latest updates for Snow Leopard.
Be sure to make a Backup of your Current System Before Upgrading...
Get yourself an External Hard Drive... and create a Bootable Clone Backup of your current Hard Drive...
By far the easiest way to make such a Backup, is to use something like
or CCC http://www.bombich.com/
That way, should anything untoward happen during the Upgrade,
you will NOT LOSE ANYTHING.
(Get an EHD that is at least equal to your current Drive...)
1) Make sure your computer meets Snow Leopard technical specifications - http://support.apple.com/kb/SP575 This mostly means making sure it is an Intel Mac and has at least 1GB RAM (more is recommended)
2) Apple no longer carries 10.6 in its stores or online. Telephone Apple to purchase a Snow Leopard disc. In the USA: (800) 676-2775 (contact information for other countries: http://support.apple.com/kb/HE57)
Alternatively you can buy from online retailers but expect to pay much more than the original price which is the price still charged by Apple
3) Backing up your computer before upgrading is always a good idea.
4) After installing from the DVD, update your Snow Leopard installation using Software Update or manually downloading and installing the Mac OS X 10.6.8 Update Combo v.1.1 - http://support.apple.com/kb/DL1399
... I have one of the old really white macbook laptops...
To Upgrade to Mountain Lion... Your Mac must be one of the following models:
- iMac (Mid 2007 or newer)
- MacBook (Late 2008 Aluminum, or Early 2009 or newer)
- MacBook Pro (Mid/Late 2007 or newer)
- MacBook Air (Late 2008 or newer)
- Mac mini (Early 2009 or newer)
- Mac Pro (Early 2008 or newer)
- Xserve (Early 2009)