Remove dual boot options (or) boot choice menu in Windows

If you have recently installed new operating system in a separate partition other than the default/previous partition then the boot choice menu appears even if you have format the previous operating system.

To remove this boot choice menu, enter into the newly installed operating system and click Start > Run > type msconfig and hit Enter.

For XP users:
Select Boot.INI tab > locate the last two lengthy lines if you have two boot choices and delete the unnecessary os.

If you do not know which line to delete, compare with the third line, if they are not same for some extent [eg disk(0)partition(1)\ in third line and disk(0)partition(2)\ in last line] then delete that last line.

For Vista/7 users:
Select Boot tab > select the previously installed os in the list box (for eg:Windows 7 Ultimate (D:\windows)) and click Delete button.

Click Apply > OK and Restart the PC.

Warning! Do not delete the default/current os line, then you will never boot into the PC thereafter.