I think the role you're trying to fit, because it is moreso task oriented and not product (deliverable) oriented, is not a good fit for the websites you're describing in the comments. Aside from that -- consider something else.
I run a business. Now, please keep reading - but this is not a personal slight to you, okay? It'd be a rare, rare, RARE occasion when I allow someone who I've never seen, who lives in another country, who I am likely to never meet face-to-face, to connect to my business Windows (or other) infrastructure machines from wherever I've been told such a person is located, and then assume administrative tasks!!! That person might be the best administrator in the world but if something's screwed up and I incur a loss, I can't say, "Oh, not my fault. Blame Lars/Abdul/Kiswele/Hanna in Senegal/Budapest/Mumbai/Caracas"!!! I can't establish a chain-of-control, and would thus be held liable for any damages. I can't sue and recover those damages from someone halfway around the globe -- at least not easily.
If such a person were attached to a larger business, it might work out better - but I'm still not going to pass on much in the way of administration tasks. It leaves me far too vulnerable.
Windows admin jobs to work remotely
gets you some relevant jobs but all on generic sites. I don't have other similar freelancers in my social circle. AndStackOverflow Careers
are all for developers. – Ayan Mullick Apr 7 '14 at 23:07