sharad dhama :
hello friends please help for ubuntu installation. when m installing ubuntu-12.04.3-desktop-amd64 (intel i3 3220 3.30 Ghz ) it showing me only 1 tb hdd not any partition. i want to install Ubuntu instead window 7(64bit)
This could be because windows did not shut down correctly, try restarting windows and closing normally.
It could also be the windows was installed under EFI (setting in the BIOS) and you started Ubuntu under legacy BIOS. Choose one ot the other.
As emerald said, you could just reformat the whole drive but then you'd lose everything on the drive. There are ways...check the first two first before we get into them.