I've been using Kubuntu for 3 or 4 months without problem, but the other day, booting my computer, it just wouldn't start... So the computer is booting, but instead of accessing the user mode, they keep me on the black screen and ask for my login and password... As I do, what appears is like official information of Ubuntu, saying there's no warranty for the program, giving an email to write to if I have any problems... And the last line says: jeremie@jeremie-laptop: ~$
And then I'm supposed to write something... How can I just start using the computer?? I'm the true definition of a dummy regarding that stuff, so I have no idea... can anybody help??
Thanks a lot!!!

You probably ended up on terminal or command line as it is said in windows.
type startx and then try if you login in a graphical mode.

thank you so much for your prompt answer!
It's a good start, after doing startx, I did get into graphical mode, but the only thing I can access is the console... My desktop is just not there, not active... I was able to start firefox for example, doing exec firefox, but I just can't use my computer normally... Can I do something like exec kde or something, to bring back my desktop?? Or maybe my compu has bigger problems...
Thanks a lot!

We need to know the actual boot problem to fix it, so you don't need to boot into single user mode.