try ko po sir salamatPress Shift + F10.
Then type diskpart.
Now type the following commands.
LIST DISK (press enter) next type:-
SELECT DISK 0 (after confirming Windows 7 target HD #) (press enter) next type:-
CLEAN (press enter) next type:-
CREATE PARTITION PRIMARY (press enter) next type:-
FORMAT FS=NTFS LABEL="WINDOWS 7" (press enter) next type:-
ACTIVE (press enter) next type:-
EXIT (press enter)
Then try again.