well yeah all games will run on older windows versions but having windows 7 just means you're asking for occasional things like this, Microsoft never made a perfect OS until 8, and no one else ever will


you'll get it working, you should to post your problem on the payday 2 steam forum, open steam click payday 2 in your library then on the right it'll say link sand one of them will say forum then that will open the steam forum inside steam then you can post a thread it uses your steam account, it's a niiiice