Pls I am new to linux and I am currently running K-Ubuntu 7.10; as I am trying to run configure script for emacs-21.4 then, I have the following error:
loading cache ./config.cache
checking host system type... i686-pc-linux-gnulibc1
checking for gcc... /usr/bin/gcc
checking whether the C compiler (/usr/bin/gcc ) works... no
configure: error: installation or configuration problem: C compiler cannot create executables.
So I am stuck and I don't know what else to do.
Tunene.

Why are you trying to install Emacs from source? Why not just install it from Ubuntu's repositories? "sudo apt-get install emacs" should do it.

Tunene, In most Linux distributions there are large libraries of pre-built software which are available to install with very little hassle. This is usually handled via some sort of "package management" system, which does installation, uninstallation, updates and so on.

In the case of Ubuntu, there are a few different front ends to the package management system. There is a graphical program called "Synaptic", which is available from the System -> Administration menu at the top of the screen.

Inside Synaptic, click the search button from the toolbar. Search for emacs. You will get a lot of results in the top pane on the right side of the window. Scroll down until you see a line for a package called simply "emacs". Click on the box at the left of this line, and select "mark for installation" from the menu which pops up.

You will then see a window saying something like "Mark additional required changes". Click the "Mark" button.

You can select lots of different programs using this procedure.

When you've selected all the new software you want to install, click the "Apply" button on the tool bar. You will see a dialog which says, "Apply the following changes?". Click the "Apply" button in the dialog and the software you requested will be downloaded and installed for you.

The instruction which Nylex posted is a handy way to accomplish much the same thing from a terminal - handy if you are in the habbit of using the terminal, or are logged into a machine remotely using ssh. Both Synaptic and apt-get are interfaces to the same underlying package management system.

Whenever you want to install software, you should search for packages like this first. Installting from source is a big pain in the backside, and is rarely necessary - the repositories are very large.

In Synaptic's Settings [menu] -> Repositories dialog, you can enable extra repositories containing many packages which are created and maintained by the Ubuntu community. This gives you access to something like 23,000 packages in total!

Well thanks guys.
When I tried sudo apt-get, the reply was that I should enable something called "Universe" which I don't know how to do it.

Also, I just realized that there is no "Synaptic tool" under system administrator tool; what I have is the "Adept Manager", but this doesn't has "emacs" listed.

If I am not mistaken, Adept and Synaptic both act as front-ends for apt-get. So you should be able to add repositories in one of those and have them work with apt-get.
If you don't like Adept, you can at least use it to install Synaptic.

You can also browse thru /etc and find the file that lists the repositories. On my system, it's /etc/apt/sources.list

Universe is a repository which by the sounds of it contains emacs. You can enable it using Synaptic as described in the last paragraph of my previous post. In the "Ubuntu Software" tab, check next to "Community maintained Open Source software (universe)".

Well thanks everyone I finally got emacs and other packages installed after I enabled "universe" and "multiverse" through Adept Manager; then I run sudo apt-get install emacs21 ... then it works right.