How to upgrade ubuntu 7.10 to 8.04 or 9.04, because now days update is not possible for ubuntu 7.10.
You can only directly upgrade to Ubuntu 9.04 from Ubuntu 8.10 for more info see: https://help.ubuntu.com/community/UpgradeNotes
Backup your /home folder. then do a fresh install of 9.10 so you can benefit from the grub2 bootloader and new EXT4 filesystem by default.
Ubuntu 9.10 Karmic Koala release candidate comes out Thursday. You can use the latest daily image now from http://cdimage.ubuntu.com/daily-live/current/