At some point M$ allowed the free download of something called “Windows XP Mode for Windows 7”. It was some virtual machine or something. What matters is that it’s possible to extract an XP ISO from this, which I have successfully used to spin up a virtual machine! It still complains about a license key, though.
The reason I mention this is that this is still available on archive.org, and it’s signed by M$, so you know it’s legit. I don’t know if other ISOs available have such a receipt of authenticity. Probably, but I never cared enough to check, especially since I grabbed this from the official website while it was available.
ProfessorProteus