If u have installed Ubuntu over an kubuntu or vice versa , u may switch over gdm to kdm or kdm to gdm .This can be done in simple steps .

GDM (GNOME Display Manager) is a highly configurable reimplementation of XDM, the X Display Manager. It starts the X session and shows a login window to the user.

On a single user system i like to have the same background for bootsplash, login screen and desktop. As the new xsplash and gdm in ubuntu karmic (9.10) makes this easy to access.

he Ubuntu design team have published mock-ups of the proposed Ubuntu 9.10 Boot and GDM screens.

In a post on the Ubuntu-art mailing list, Mat Tomaszewski revealed the proposed designs, and confirmed the plan for Ubuntu to use a new boot-screen manager, replacing Usplash with Xsplash.

Create your own login screens in ubuntu..Components of a GDM ThemeA GDM Theme is basically composed by:*

For years now, I have been clinging to xdm as my display manager; years ago, I spent several days tweaking the configuration files of xbanner and xdm to get it to look “just so”, and I didn’t want to change it. But no more! After my last upgrade predictably broke my xdm and xbanner configuration, I decided to spend a little time trying to get each display manager to look “right” with my original login screen design. Pleasantly, both gdm and kdm are much easier to customize, and I had something tolerable with each in less than an hour. I found that kdm was more flexible and gave me much closer to what I was looking for, while gdm was quite obstinate about appearances, though it may be slightly more capable technically.