secuono; Hi !
+1 to whitesmith's last. However, there are means to upgrade an end of life version online. Be advised it will be heavily fraught with the PROBABILITY of errors with all the changes that ubuntu has undergone in the past years ... and will take hours and hours to do so. The process is from one version to the next version to the next version...8.04 to current 13.04 is 10 versions.
IF you are really intent on attempting this course; the documentation:
you will need more than luck