hi,
I am very new to the linux world.
I have a Lenovo 3000 N100 laptop which LCD does not work anymore.So I borrowed a monitor from my friend and started using it(it has been few days).I had installed Fedora-12 few months ago. After connecting the external monitor, I found that this one shows good graphical start-up but just upto the login screen(just before the login screen, login-screen does not come) and it proceeds no more.Though I can get the virtual consoles restarting xserver is of no use.

Please help me to find out any issue.

Some times you have to press a key combonation.
Try FN+F3,FN+F4,FN+F5 and FN+F6.

ohhh, how simple the solution was.
Thank you for your help.

But I need to do that every time I start-up. Is there any other way around?

Try do access some display configuration dialog.
It should have a default moniter setting there.

you could edit /etc/X11/xorg.conf

be sure to make backups as this can cause headaches.

there's a lot of tutorials out there.

You might be able to change settings through GUI but I a command line commando :-p