Depends on how much you value your time and frustration dealing with the crapware that came with the OEM installation. You can often buy hardware without Windows installed, save the Windows tax, and install a clean copy bought elsewhere.
When you use Windows, you must be prepared to pay, and pay some more, and then spend inordinate amounts of time fixing and cleaning and repairing. Or risk malware with "cracked" versions to save a few bucks.
Personally, I prefer to run my Windows in VMs (virtual machines) hosted on either Mac or Linux workstations. That said, I have three Windows installs "on the metal" at home, dual booted.
That's what I thought you meant but your comment in #5 led me to believe the PC had been bought with an OS.