Welcome to LQ!!
You have posted this into a thread that is almost 2 years old, and which was started by someone confused about GRUB (the bootloader). I will report this and get your post split out into a new thread.
What you are calling the "environment manager" is most commonly called the "desktop environment" or simply "desktop". Fedora comes with Gnome, and KDE is the other most popular one.
You don't say how the computer got set up with KDE---it is likely that Gnome is still there. If so, you can switch using the login manager: Simply hit ctrl-alt-backspace to restart X. When the login window comes up, click on the session tab and select "Gnome". Enter your name and password normally and you will be placed in Gnome.
If Gnome is no longer installed, you can get it using the package manager, or you can simply install a later version of Fedora. 9 has been out for a while, and 10 comes out today.