Modern Warefare 2 Spec Ops Partner?

Sup, I play Modern Warefare 2 on steam for the PC and I recently became interested in Spec Ops. I'm not bad, I got 3 stars on everything in Alpha in a couple of hours, but it's steadily getting harder and some missions it won't let me do without a partner. I'm friends with a lot of people who have Steam, but none of them play modern warefare 2. All the friends of mine who play it play it on xbox. I've played split screen Spec ops with some of my friends on xbox, and it's a ton of fun, so I kinda feel like I'm missing out because I own the game for the PC. Any help?