everything went fine....moreover the drivers also got installed ..
it shows "building all kmod of nvidia failed"
There is some contradiction there, no?
As I pointed out, you go here:
and you download the Fedora 8 repository rpm to your desktop.
Then you open a terminal and you do:
(type root password)
rpm -ivh livna-release-8.rpm
yum install kmod-nvidia
That's it. Now, as for the issues you are having, those seem to be caused by not following the proper procedure. The first thing you should do is try and remove any parts of the nvidia driver that were already installed and then run yum install kmod-nvidia. However, if things go mixed up badly enough for that not to work, you may need to reinstall all of X, which is not exactly an easy thing to do. You may as well do a reinstall if you are not familiar with Fedora yet.
Enabling compiz is rather easy. If you use Gnome, just go to System > Preferences > Sessions and click on "Add". Type compiz for title and compiz for command, then log out. This is the ideal scenario but you may find that it takes more effort to enable compiz with specific types of video card (some ATI in particular).