Try chucking a boot cd in and running a fsck on your hard disks
fsck.ext3 /dev/hda3 (or whatever depending on file system and where your linux disks are)

you can boot the linux from grub prompt by pressing c and find root and boot partition there. after that boot from grub. i think /etc/grub.conf file has been changed.if you have any problem mail me further bidyut.vision@gmail.com.

Hey! I've got a problem that I hope can be resolved. I've got a linux system from br in- law .After synaptically getting some games, I tried one out(flying game) and the window, which wasn't maximized at the time, would not close and the rest of the functions seemed frozen and unresponsive. I rebooted and instead of my usual login screen, there were odd, misplaced graphics in a checkerboard pattern filling the screen up to half from the bottom up.
The login sound isn't heard , the login screen doesn't apppear and instead of 1 UBUNTU graphic logo, there are two smaller ones, their graphics being sketchy.
There is nowhere to login or anyhting the screen just stays like that

I think that is configuration prob visit this link www.aumha.org/win4/a/shutdown.php
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I Suggest you if you have any idea about hardware
then open your pc & remove your RAM & CMOS Battery after 5 to 10 min. just fit it
Now try to start your pc........