Microsoft provides the Windows 10 update for free only until the end of July 2016, after this date everybody has to pay for it. But if one still wants to keep the existing ("old") operating system, Windows 10 can also be installed as a second operating system or as a virtual PC. With a special tool from Microsoft you can download the installation files and install it as a new operating system, as second OS with a dual-boot manager or as a virtual PC.
The installaion of a virtual PC, e. g. the free of charge VirtualBox, only makes sense if your system has enough hardware resources. If the processor isn't efficient enough and doesn't provide the appropriate memory capacity, working with the virtual Windows 10 isn't really possible. Then a dualboot system would be better, but this also requires space at the hard disk.
With the media creation tool the files for the setup can be downloaded as ISO file or for the USB stick for later installation. A product key for the new Windows 10 currently is not required, this means one can use the key from the sticker of the existing Windows 7 or Windows 8.x. When installing Windows 10 as a virtual PC of course an other basic system like Linux or OS-X can be used also.
Actually it is not clear how Microsoft will handle the licenses after July 29, 2016. There's just one month to go to get a free of charge update, also for those who don't want to get a complete update installation of the old system.
We would be pleased to consult you about the possibilities for your system and of course we will make a complete backup of your files and data before installing a new system.