How to make sure that a certificate and a private key match together?

This link gives you commands to do what you want: http://kb.wisc.edu/middleware/page.php?id=4064

Those commands should work in a Windows installation of OpenSSL.

autocompare doesn't work in Windows, and I don't really understand what numbers to compare

00:b6:9e:3b:75:4d:f2:12:4b:43:a1:aa:64:79:41:
                    f3:dd:bd:b6:bf:14:bb:05:3f:72:ed:12:c6:d2:5e:
                    9c:72:2c:52:35:93:30:a5:5c:0f:e8:1c:ce:32:ea:
                    7a:61:f8:85:dc:82:50:ef:7e:f2:ab:b1:7a:31:05:
                    76:73:cb:20:8b:af:dc:d0:5b:dd:1a:26:ab:46:e3:
                    3e:0e:e1:a3:01:41:bc:d5:2f:60:08:d5:2f:12:3b:
                    7c:20:5b:3a:2e:66:cd:42:40:72:52:53:52:93:e3:
                    b2:2f:bd:74:08:fd:57:ca:58:34:b4:96:b0:ed:26:
                    ed:a4:f7:63:d1:2b:02:83:11

And

00:dc:15:6c:81:e7:e1:c6:ad:ef:42:e9:47:f1:20:
    83:cf:85:a4:df:8c:26:b1:00:37:54:e5:b4:e0:bb:
    8d:a8:d1:9f:1f:a4:29:7c:08:4f:c5:38:97:b0:bf:
    ea:80:81:91:90:d3:00:8f:e6:c2:29:e1:66:6a:ed:
    08:e1:90:10:4d:77:37:7d:01:8a:cc:e3:46:16:ab:
    3b:4f:99:c8:61:85:59:87:1f:7a:47:4e:bb:e1:47:
    6c:30:c8:e0:d1:fc:01:ed:8e:e4:e2:fe:a4:a1:48:
    73:18:e7:d8:76:36:d6:e7:7c:6a:1c:e8:5d:25:11:
    04:69:5e:94:ec:f3:51:28:b5

So, this is a wrong key, right?

From what I can see, yes.  But just be sure, you can try the commands on a known matched certificate and key to confirm you are not looking into the wrong place.

Superb!