If you are going to purchase windows 7 OS from Microsoft Store, then microsoft provides you option to download an ISO file or compressed files. The Windows 7 USB/DVD Download tool allows you to create a copy of your Windows 7 ISO file on a USB flash drive or a DVD. To create a bootable DVD or USB flash drive, download the ISO file and then run the Windows 7 USB/DVD Download tool. Once this is done, you can install Windows 7 directly from the USB flash drive or DVD.
The ISO file contains all the Windows 7 installation files combined into a single uncompressed file. When you download the ISO file, you need to copy it to some medium in order to install Windows 7. This tool allows you to create a copy of the ISO file to a USB flash drive or a DVD. To install Windows 7 from your USB flash drive or DVD, all you need to do is insert the USB flash drive into your USB port or insert your DVD into your DVD drive and run Setup.exe from the root folder on the drive.
→ Windows XP SP2, Windows Vista, or Windows 7 (32-bit or 64-bit)
→ Pentium 233-megahertz (MHz) processor or faster (300 MHz is recommended)
→ 50MB of free space on your hard drive
→ DVD-R drive or 4GB removable USB flash drive
You can download Windows 7 USB/DVD Download Tool from here.