If you take advantage of the free upgrade to Windows 10 from Windows 7 or 8.1. This offer will be available after July 29, 2015, and will only be good for one year after that date.
Microsoft has recently announced that you will be able to perform a ‘clean install’ of the new OS after you upgrade on the same device at any time. This is good news for people who have a system that has a lot of clutter (i.e. unnecessary programs) or is infected with malware and they want a fresh copy of the OS.
For those not familiar with the concept of performing a 'clean install' of the operating system. This process involves formatting the storage device on the computer and installing a fresh copy of the OS. This helps to eliminate issues that can surface during this process. It's also an easy way to configure everything the way you like it.