Hi buddy,
Before thinking about how you can convince others about your transition from IT to HR (which is indeed quite drastic), you must be convinced yourself. In your heart of hearts, if you know that you feel more passionately about HR, then it would never be a problem in explaining to others. Only if you genuinely and strongly feel about it, it will come across quite clearly and effortlessly.
If you know why you want to switch over to HR, I am sure it would never be a problem explaining to recruiters. It's quite simple. Maybe you took IT because of family pressure, or maybe because you yourself never knew that you would enjoy HR functions more. So, maybe you can say that after working for 2 years in IT, you realized that IT is not what you feel passionate about, and you have now realized that HR is more of your kind of thing. You know, so...
One of my HR faculty had done his MBA from FMS in marketing and worked as a marketing professional for a long time. But later, he realized that HR is more like him, so he switched over. Today, he has more experience as an HR person, and trust me, he couldn't have been more satisfied. If you want, maybe I can try to find his phone number, and then you can talk to him if you want.