Please help. I'm a novice with no clue about what to do.

I don't remember exactly what I did, but all I did was change settings in compiz. After restarting my computer, my screen is completely blank, BUT I can still log in. It is still blank after that though.

I don't know how to fix it and I was hoping I could fix this without having to lose everything I've done already.

Thanks

is there a way I could turn off compiz without being able to see what i'm doing? I know it must be possible in terminal, but I have no idea how to go about doing it.