Using a VM to test a key loses one of your 10 activations, if the key has been used several times (I've been burned buying used XP Pro OS's with keys, twice), you can lose your last activation in doing so. Many of these keys have been activated 9 times (or more). Which will prompt you to call Microsoft anyway, unless you enjoy looking at a black screen.
Not to mention that you can only get security updates. No WMP, no Windows Live products, no MSE or Windows Defender, you get the picture. Today, unless it was someone who I personally knew, and trusted, I'd never buy a used OS again. I was fortunate that I got my money back through my PayPal protection. The sellers sold my VL keys & provided me a link to D/L the OS, which are not to be sold under any circumstances. I was unable to complete activation, and MS was unable to help me.
However, MS did offer me a full XP Pro SP3 package for $89 + tax, which I accepted. But it was not a D/L, it was sent by delivery confirmation through USPS. It arrived in 2 days. But this was in 2009, I doubt that they'd do that now. If someone who bought a counterfeit XP OS, they have the chance to "become genuine" for whatever price that MS offered the user.
I realize that this is an old thread, but my post can provide information needed to someone in the future.
Cat