Before you upgrade to the latest version of Ubuntu, you should check if your computer is compatible with Ubuntu by reading the system requirements which you can find at Ubuntu.com . If your computer is fast enough, you should not have a problem installing the latest version of Ubuntu on your computer. You can also use the Ubuntu Live CD of the latest version, and test it out on your PC from starting your computer from the CD to test it out before you install to make sure it runs well on your PC.
The simplest way to upgrade Ubuntu Linux to the Latest version of Ubuntu Linux is by using the Ubuntu Update Manager which gives you the option to upgrade to the Latest version of Ubuntu Linux when it is available for download. This means you can keep all your Apps, data, and folders if you use the Ubuntu Update Manager to update to update to the latest version of Ubuntu Linux.
You can also start your computer from a copy of the latest version of Ubuntu Linux CD, and upgrade through the CD.
To be on the safe side, you should back up all your important files like photos, video, documents, work, and other files to CD-R, DVD-R, USB Flash Drive, or another drive in the rare case you lose all your data because of a failed upgrade.
The best way to upgrade to the latest version of Ubuntu is to do a clean install which means the Ubuntu CD will delete your old version of Ubuntu to install the newest version of Ubuntu on the CD. However, you lose all your 3rd-party programs, and data, so backup your data, and make a list of programs which you need to reinstall from the Ubuntu Software Center after the install after you finish installing Ubuntu from the CD, and updating Ubuntu.
Make sure to update Ubuntu after you installed the latest version of Ubuntu to install updates to fix bugs, and performance problems with Ubuntu by running the Update Manager program in Ubuntu to install fixes and patches by running Update Manager in Ubuntu Update Manager.
To learn more about Ubuntu Linux, I recommend that you buy a copy of Official Ubuntu Book, The (5th Edition) to learn all the advantages of Ubuntu Linux 10.04, and how you can use Ubuntu in your daily computing needs like office work, photos, entertainment, internet, e-mail, and multimedia.