Many times your Windows PC Desktop/laptop/notebook/netbook or ultra book comes preloaded with Windows & there is no Windows installation disk comes with your laptop but there is a COA label on your system containing your Windows Product key. Some people think that only option left is either to make a recovery DVD on the first day of your purchase or to keep running the Windows Installation that came preloaded with your machine, Not necessarily..
Your preloaded Windows system comes with a Windows Product key or commonly known as CD-key. Keep safe of that key.
Note down the Windows Edition that your using. The version are:
Windows 7 starter
Windows 7 Home Basic
Windows 7 Home Premium
Windows 7 Professional
Windows 7 Ultimate
Now note down your system type:
Refer screenshot below and make a note of what your system type is 64 bit or 32 bit.
Note: Your product can be used on both x64 (64 bit) & x86(32 bit ) Operating system type.
Note: You should use 64 bit operating system only when you have 4 Gigabytes (GB) or more RAM.
How to get a Windows Installation Disk:
You have your Windows Product key and you are a genuine Windows user:
Download ISO file for your Windows Edition & system type below:
Make your you download the right edition with right system type, x86 (32bit) if you have less than 4 Gb Ram and x64(64 bit) if you have more than 4 Gb Ram.
Windows 7 (English) with Service Pack 1
• Windows 7 Home Premium (x86) – X17-58996
• Windows 7 Home Premium (x64) – X17-58997
• Windows 7 Professional (x86) – X17-59183
• Windows 7 Professional (x64) – X17-59186
• Windows 7 Ultimate (x86)* – X17-59463
• Windows 7 Ultimate (x64)* – X17-59465
Burn the downloaded ISO file with either double clicking it and using Windows 7 Image burner or any third party CD/DVD burning software.
*You will need a BLANK DVD Media to burn this ISO file or follow this guide to Install Windows 7 using a USB Pen Drive
If you use a DVD, boot from it & when asked for product key, insert your product key located on the COA label on the bottom side of your laptop or sometime behind the battery pack.
Activate & enjoy.
For More Information : Microsoft Answers Forum