Installation process is largely the same across most Linux distributions.
The biggest difference between 12.04 -> 14.04 is driver's for newer hardware, newer kernel, newer software including UI improvements
How i install (keep your windows harddrive plugged in):
1) Burn iso to CD or use LiLi to make liveUSB of Ubuntu http://www.linuxliveusb.com/
2) Boot from usb / CD
3) The installer will guide you through the process. (partitoning, install bootloader, keyboard setup/language etc). Take care to make sure you install to the correct drive!
4) When installing the bootloader, Ubuntu will "automagically" detect your Windows 7 installation and add a Windows entry to the boot menu. This will allow you to choose Windows or Ubuntu when booting.
5) Reboot and set UEFI/BIOS to boot from your Ubuntu harddrive first.
You can find many guide on youtube if you want video