It is time to replace 10.04 since, as you have already been told by rokytnji, it is no longer supported.
First, backup all your documents, photos, emails bookmarks etc to an external hard drive or USB stick.
Then, depending on your RAM and CPU, download and install another distribution such as Ubuntu 14.04 MATE, Linux Mint 17.1 MATE, Zorin OS 9, Zorin OS 9 Lite etc etc.
There are plenty of very good reviews on Linuxed for different distros:
Also, there is no need to install one of them immediately, just use a live DVD to explore its main features.