[Nottingham] lost kde after changing display settings

[Sarah Swindell]

I tried changing the display settings in KDE (I think I ticked something 
like "support NVIDIA drivers". I realise with hindsight that this was a 
mistake) and am now only presented with a command prompt "tty1" asking me 
for my username and password. I can't get KDE to start up at all.

I've signed into the tty1 prompt but have no idea how to change the display 
settings back. I've had a look into the help topics but am none the wiser. 
(The only command I know is "LS" which I don't think is going to help.)
I am hoping to avoid having to do a fresh install of linux (Mepis, Debian 
based).
any ideas how to fix it?

Thanks in advance,
Sarah