One recent headache of mine was to test windows programs safely, or just to run some proprietary program, like a closed source VPN, in a VM.

In the past, Microsoft offered a cheap Technet Subscription for people like me. That allowed us to download Windows images, and to deploy as many VM's as we needed. As part of turning their back to users (Windows 8 horrors, Windows 10 morphing into spyware, terminating the high ranking Windows certifications), Microsoft terminated the Technet subscriptions.

The only commercial available alternative today is MSDN. Where I live, that costs almost three average months income, and is not an option. Seriously - I have not worked commercially with Windows for ages. Even when I worked for one of the largest software development companies in the USA last year, my workstation had Debian Linux on it, and my software was targeted for Redhat Linux. (Only the floor level managers used Windows - the rest of the management used mostly Macbooks). Personally, I support the Windows platform for some of my free software mostly for sentimental reasons.

Anyway, there is a site that provides legal Windows VM's for several hypervizors, including VirtualBox:

The licenses expire after a few months, but that's OK for just testing some software.