If you’ve lost your Windows DVD, or you never had one, you can still reinstall Windows 7 without it. Here’s how.
How to install Windows 7 without the serial number
First, you need to have your Windows licence number or, to use its correct name, the product key. This might be printed on a sticker somewhere on your laptop or PC, or on some documentation provided with it.
If you don’t have this, or you’ve lost it, you’ll need to have access to Windows running on your computer. The reason being that you can get the product key using a free utility called Magical Jelly Bean Keyfinder. This can also extract keys for other software.
You won’t be able to get the product key if your hard drive has broken, or if Windows is corrupt and you can’t get it to boot, or you can’t log in.
How to install Windows 7 without the DVD
Assuming you have the product key, you’re sorted, as it’s easy to download the installation files for Windows online. You no longer need to know exactly which version of Windows your product key is for.
Step 1. If you want to find out which version your computer is running go to the Control Panel, then System and Security, and finally System. Along with other information about your PC or laptop, this will tell you precisely which version of Windows 7 it is. Keys should work with either 32- or 64-bit versions of Windows 7, but you can’t swap from Windows 7 Home Premium to, say, Windows 7 Ultimate.
Step 2. To download Windows 7, head to Microsot's website to download the correct version of Windows 7.
Step 3. Now you have the software you need to burn it to a DVD, or extract it to a suitable USB flash drive. You can’t simply copy the ISO file to a flash drive or DVD. Instead, you need a tool to do this, such as Microsoft’s own USB/DVD tool Microsoft’s own USB/DVD tool
Alternatively you can use the tool we recommend in our guide: How to install Windows 7 from a USB flash drive.
Step 4. Shut down your computer and insert your DVD or USB flash drive. Now power on the PC and it should boot from the disc or drive. If not, you’ll need to enter the BIOS and change the boot order to prioritise the DVD drive or USB drive.
Step 5. When you get your computer to boot from the disc or USB drive, you can install Windows 7. Be careful, though. If you’re planning to do a fresh install and format the hard drive as part of the process, make sure you’ve backed up all your documents, music, photos, videos and other files you don’t want to lose.