Nothing legal.
That's the choice you make when you choose to run Microsoft products. If the advantages outweigh the disadvantages, then it is the right decision for you.
The advantage of open source is that there are no licensing issues. To me, that is a tremendous advantage. That does not mean I expect it to be for you, but I bet someday it might be because (some) open source is approaching the ease of use of Microsoft.
You ought to try Knoppix.
If you have a serial modem (not a WinModem) it will find and configure that, as well as all your other hardware, and it does it without being installed. It runs from virtual memory, so it does not disturb your present system in any way.
I have found it to be a great rescue disk for laptops that have crashed. You can bootup in Knoppix while connected to a network, then copy all the user's data to a network drive.