The optical drive tends to be the slowest part of your system. So why use your DVD-Rom drive to install windows operating system when your USB flash drive is much faster ? Microsoft has come with a solution to address this problem, a very small piece of software: Windows7 USB/DVD download tool.
So what actually does Windows7 USB/DVD download tool ? The answer is very simple: it takes a copy of Windows installing DVD in the form of an ISO file and places it on an USB flash drive. What you have to do next is to just boot from this USB stick instead DVD and proceed with Windows installation as normally. If you can't find in your motherboard BIOS the option to boot from an USB flash drive, than just press F11 during booting and choose from there your boot option (it works for most motherboards, just press the corresponding F to open boot manager). If you don't have the ISO file for your Windows OS you can make one with specific programs from CD/DVD tools section here.
Windows7 USB/DVD download tool give best results if you have in BIOS SATA enabled as ACHI instead of IDE compatibility mode.
download free Windows7 USB/DVD download tool