Fedora 15 gnome problem

[fedorauser]

I used two helpful tutorial's on how to boot Fedora within VirtualBox, and when I finally got it to work it said " automatically booting in 3... 2.. 1.. " something like that. and then it just booted without any login screen and it said gnome 3 couldn't load because my computer didn't have the right graphics, etc. and I clicked OK and it just looked clunky and not how it's suppose to be. And I tried enabling 3d acceleration graphics but nothing, and when I try to install guest additions it says
" Cannot mount this disk ". Is there any way of there being a login screen, which you can create your own user on, and how to fix the clunky design?

[stefan.becker]

Use newest version 4.0.10 and install in Fedora the newest guest additions.

[fedorauser]

How do I install Guest Additions in Fedora? and I'm pretty sure I installed the latest version from the " Downloads " page just today.

[stefan.becker]

Look into the tutorial section / linux guests.