i made dual boot of Windows 7 and Ubuntu 14.04,but after installing the Windows Drivers the Computer is not showing the option to choose between Windows and Ubuntu..it is directly moving to Windows..Why???
Do you mean after installing the windows drivers, or after installing Windows? My guess is that you installed Ubuntu first, then Windows, and after installing Windows you saw this problem.
Windows doesn't know about the GRUB2 bootloader (the menu used to select between different operating systems) and writes its own bootloader when you install it.
You need to reinstall and reconfigure GRUB2. This looks like a reasonably detailed description of how to do it, but there are other ways (google, now you know what you're trying to achieve) if that doesn't suit you.
I think you have installed ubuntu first and than windows. If Yes, then you should go with the software Boot-Repair-Disk http://sourceforge.net/projects/boot-repair-cd/ Boot-Repair-Disk is a live CD that repairs multiple Linux distributions. Boot-Repair Disk repairs the GRUB boot loader of Linux and can repair multiple editions of Microsoft Windows operating systems. Instructions to use Boot-Repair-Disk are on links below https://help.ubuntu.com/community/Boot-Repair