Support for Windows 7 ends on January 14th. After this point, there will be no new patches. Should hackers manage to find a new exploit, your unsupported computer will suddenly become very, very vulnerable!
Although the free Windows 10 upgrade expired some time ago, it would appear that it can still work in some circumstances. Microsoft have said they will close this loophole when support for Windows 7 runs out.
To upgrade to Windows 10 you need your Windows 7 product key. This might be with the media that came with the computer or it could be on a sticker on the case. The simplest way to find it is to download and install produkey from nirsoft. While you are there, there are a number of tools for scanning your system for passwords. Make sure you copy any keys off the computer as you won’t be able to access them at install time.
The next step is to download the Windows 10 media creation tool. With this tool you can upgrade the current machine or create Windows 10 install media on DVD or USB to install from.
The method that seemed to work was to create a bootable USB device using the default options. Reboot the computer and tell the BIOS you want to boot from the USB device. At this point you will get the option to enter your product key. If accepted proceed with the install, if not, just back out of it and either find a different key or perhaps look at installing Mint Linux!