Need more speed...I have a iMac OS X, version 10.4.11

First, to upgrade to the latest Mac OS X you have to build on Snow Leopard, 10.6.8. So the minimum purchase would be SL from the Apple on-line store for $20 for the installation disk. Then on-line software update to 10.6.8 from the disk version, 10.6.3.

You would then have to decide to stay with SL or move to Lion or Mountain Lion. By the way, SL is a very good operating system, but it does not have iCloud so if that is important you would look at moving furterh.

Lion requires at least an Intel Core 2 Duo, i3, i5, i7 or Xeon processore, 2 GB ram (runs much better with 4 GB) and 7 GB hard derive space. Avaiable by calling 1-800-MY-APPLE and purchasing the download code for the Mac App Store for $20.

To move to Mountain Lion you have to meet the specs of http://www.apple.com/osx/specs and can purchase directly from the Mac App Store. You do not need Lion to go from SL to ML.

Find out some info. about your computer first. Click on the Apple, and select "About this mac"

- what is your processor type

- how much memory (ram) do you have?

Leopard System Prequirements - (10.5) - http://support.apple.com/kb/sp517.

This operating system is quit old, and you would need to seek it out on places like "ebay" or "amazon"

See if you system will take these first......

Snow Leopard System Requirements (10.6) - http://support.apple.com/kb/SP575.

Lion System System Requirements (10.7) - Mac OS X 10.7 Lion System Requirements

Mountain Lion System Requirements (10.8) - http://support.apple.com/kb/HT5444.