i have tried dual boot win7 and ubuntu 12.04 -details bellow
1)1st win7 was installed
2)in extended partition- with root and swap partitions ubuntu 12.04 was installed from live cd.
after completion of the ubuntu install on reboot got the boot choice screen --on selecting either win7 -nothing happening
--on ubuntu selection-got the screen with username/passord screen but on entering the same nothing after that only black screen with cuusor,
1)tried to use the boot-repair command after installing the same thru live cd, still nothing
2)tried super grub live cd--attempted to repair, got the windows7 loading, but the ubuntu is still doing the same--
that is, after entering the user name/password -only black screen. can you suggest what corrective actions to take please?-pravin

Provide information on your hardware, particularly graphic card.

You might try a sort of fast-fix:
Boot the LiveCD
Mount the Ubuntu partition: sudo mount /dev/sdaX /mnt (X being the Ubuntu partition number)
Run grub-install: sudo grub-install --root-directory=/mnt/ /dev/sda
Reboot, then run sudo update-grub

i tried this, but after first line of command the display said==unable to find sda5 look in , the main words were-- etc or fstab
while i am able to manually mount the sda5 and the installation folders are visible there.
also i tried to do boot-repair thru live cd. and the end note said quote this for further advice
==http:://paste.ubuntu.com/973948==
also after the boot-repair finish tried to select load unbuntu option on boot choice screen ==it advanced upto the username /password input screen on entering the username/password --black screen with cursor.

Maybe it would help to see what is actually on your hard drive in the way of partitions. To do that, you can boot the LiveCD, and in a terminal run:
sudo parted /dev/sda print
That will give you the view of what is where on your hard drive, so when you do the fast-fix you can pick the correct partition.
By the way, I hope it isn't a matter of hda vs. sda?

Or sudo fdisk -l...
Also, this is possible if you a video card does not identified correctly. Do you have a file /var/log/Xorg.0.log? If so, provide it, please.

before installing, i tried it in the live cd and all operations were normal ,
and have to go out of town for 2weeks due to my my work schedule, will revert back after that. -pravin

hi, back home today.
tried to do as suggested, got this back on the screen
on: sudo mount /dev/sda5/mnt
cant find /dev/sda5/mnt in /etc/fstab or /etc/mtab
2)also tried to run fdisk -l
report is attached
if i open sda5 manually the ubuntu folders are visible there

Attached Files

ubuntu_screen.txt (1.2 KB, 18 views)

You entered the above command incorrectly which is why you got the message showing. Correct way needs a space before /mnt like:

You seem to be able to do this already. If you are using the Grub bootloader for Ubuntu and get to the login screen from its boot menu, it is probably not a bootloader problem. More likely graphics. Try running the command below to get output on your graphics card to post:

tried to do that, but i got some error,
on 1st attempt the note said confirm the device for grub is mounted--then i had typed sda5-- so tried again with only sda but the note said it is already mounted.
tried to run the update grub command--no success
what i typed and got back is attached.
2) in the 2nd part of advice--for the details of graphic card--the command includes a verticle line or bar --how do i type that--please explain.
==ppm

Attached Files

report1.txt (557 Bytes, 10 views)

The problem you initially reported was not being unable to boot Ubuntu from Grub. You said you could boot Ubuntu but had a black screen. I don't see how reinstalling the Grub bootloader is going to change that.

If you are using a Live CD of Ubuntu to run the update-grub command, it won't work. It's a read-only filesystem and to reinstall Grub, use the command given above by albinard. You need to make sure it is mounted as you need to mount every time you reboot. In the txt file you posted, this was accomplished using: sudo mount /dev/sda5 /mnt

Again, Grub doesn't seem to be your problem as you indicated from the beginning you could boot Ubuntu but could not see the screen.

On my keyboard, American-English it is above-right of the Enter key. You need to hold the shift key down at the same time.

Do you have 2 windows 7 installations?
Was the 2nd installed after ubuntu as the partitions labels show a wins 7 installation at sda8.