I'm trying to install KDE with synaptic manager on ubuntu but i get this error every time.. What does it mean? Why can't i install? It installed a lot of things but some things it said it can't..

http://www.freeimagehosting.net/uploads/eb1fa0839e.jpg

Seems pretty clear to me: "404 not found". For some reason synaptic can't find and download the packages you want to install.

Maybe your repository source list is wrong somewhere, or maybe there's some kind of server outage upstream and it can't send them to you or something.

One thing that sometimes happens is that when new packages get uploaded to the various server mirrors around the world, the filelist get updated immediately, but it takes a longer time for the actual package data itself to copy to the mirror. If you just wait a while and try again occasionally you might find that more and more package become available over time.

For reasons like this, I usually set synaptic to "download packages only" the first time around, and then only after I have all the package data downloaded do I turn it off to run the actuall update.

Hmmm.. maybe i need to update repository list? How can i do this in synaptic? I don't see any update buttons anywhere..

If you go to the actual site referred to in the error messages the answer is clear - because the packages that synaptic is looking for aren't there. For example the first package on the list is:
jockey-common_0.5~beta3-0ubuntu6_all.deb but the package in the repo is called: jockey-common_0.5~beta3-0ubuntu6.1_all.deb. No wonder it can't find it. It's misnamed.
You probably need to run update on synaptic. It should be found in the "actions" menu (if synaptic has one). Life is some much simpler on the command line. ;-)
Cheers,
jdk

Oh yeah.. you are so right about that one

I ran sudo apt-get update
Then sudo apt-get install kubuntu-desktop

and it seems to be intalling fine so far.. YAY!!!

btw, it asked me for some kind of manager kdm / gdm which one to choose??

Whichever one you like They both work fine. I use kdm but linux is about being free to do what you like. You can try both and then stick with the one you like.
enjoy!
BTW, you might want to try aptitude instead of apt-get. I bet you'll like it more.
jdk

I don't even know what they are and what's the difference between them.. Can you tell me?

They are display managers (hence the ___dm in the name). When your X-server first starts, these are the guys that give you the splash screen and the place to login; the first graphics bit that you see on bootup. If you're ever curious about what a package does, try on the command line. It will give you a quick synopsis of the package including what it does.
The difference between gdm and kdm is mainly cosmetic. Their functionality is pretty much the same.
Cheers,
jdk

kdm is the login manager of the kde desktop, and gdm is the manager of the gnome desktop. They both do the same thing, but only one of them can be used at a time. You should probably choose the one from the desktop environment you intend to use most often, because the easiest way to configure them is through their respective control centers. But you can choose whichever one you want, and it's possible to switch them later if you want to.

By the way, the synaptic "reload" is the same as running "apt-get update". Synaptic is mostly just a front-end for apt, as is aptitude, though there are some differences in package tracking and management between them.

OK thanks!

OK, so i did sudo apt-get install kubuntu-desktop and guess what, it installed KDE 4.1 but i wanted KDE 4.2 How can i upgrade now?

The safest way is to wait for the distro maintainers to upgrade for you. It will come as an automatic update, probably very soon.

"sudo apt-get install" gets the newest version available in the repos.

Cheers

Oh.. right i haven't installed any updates for a while now.. that could be the problem.. thanks