sir i had windows 8 release preview previously installed.
then i tried to install windows 7 ultimate from inside the windows 8.
after the end of installtion during completeing step installtion stops responding.
and my winddowss not installed andd my previously installed windddow also stops working.
and after i tried to install winodw from dvd but after all setting and drive setting when then actual installation strtts .
the first step which is coping files completes in 1 sec. and go to second step and stop responding.
for those who can't delete partitions with a windows disk need to try this , I was unable to delete any partitions and then I came across this answer ,,,,, it was exactly what I needed and it worked !!https://answers.microsoft.com/en-us/windows/forum/windows_7-windows_install/trying-to-format-my-hdd-for-clean-win-7-install/709654ef-d6fd-4686-9145-a1e4bd5ee588?auth=1