jaunty is end of life, the servers you used to get your updates from no longer exists. This is likely why you get the error message. So you would need to update the download servers in your update manager to do an upgrade to the next version.Unfortunately the follow up version (karmic) is also end of life and has been for a while, which means that you will likely not be able to do the upgrade from jaunty to karmic, as you won't be getting any packages for karmic. See also here: https://help.ubuntu.com/community/EOLUpgrades/Jaunty
This is an issue as you can't upgrade from jaunty directly to lucid (or rather you cantry to force it but it will very very likely break everything). Lucid would be a long term support version, so that, should it work, you would at least have a release that is still getting updates. However to get up to the latest release you would still have to upgrade to maverick, then natty, then oneiric to be up to date.
The next long term support version will be precise pangolin and will be released in april. (long term suport means 4 year support instead of 2).
So since you would very likely be needing a CD-drive either way, I would recommend the clean install. I think maybe the best course of action would be to wait till end of april and do a clean install (from CD, in that case)
EDIT: IT seems we crossposted. You can try to download the .deb version of gparted here: http://archive.ubuntu.com/ubuntu/pool/main/g/gparted/
and install it in command line with sudo dpkg -i filename.deb
However, a) it's likely that you'll need to do this for a number of packages to meet all dependecies for gparted and
the exact version used (0.4.3) is no longer available. Try the ones closest to it in version number for best chances of compatibility.
Maybe also check if parted is installed (command line utility) which would allow you to format the drive from the command line. (Gparted is "just" a GUI for parted)
Edited by myrti, 23 January 2012 - 02:42 PM.