If you have just started (a month) doing hatha yoga I would stay away from anything marketed as for runners or athletes, unless you feel like you need to be challenged.
My first recommendation would be to find another instructor, something permenant not a 6 week or so course but a continous class. Some of my students have been with me from the first day I started teaching 4 years ago. You will learn more from an instructor than any video. A video can't tell you if you are doing something wrong and can't explain what to do when you say "this hurts", "right here".
That said I know not everyone has time to go to a structured class. Heck, I have trouble making time for yoga and I'm an instructor. Your best bet is going to be something from the yoga journal site. It is a well written and easy to follow.
www.yogajournal.com also many of the instructors are contributors to the magizine and questions can be addresses thru the online glossaries. I also recomend Rodney Yee as a instructor that does well on tape. If you want to be challenged try Baron Baptise, Beryl Bender Birch (low quality video but good instruction) and Brian Kest. I have recommended instructors instead of specific videos for a couple of reasons. 1) I don't have the vidoes in front of me right now. 2) All of these people have various titles available right now and anything by them will fit your need. Read the descriptions, check amazon feedbacks and you will find something that will suit you.
Namaste
Jim
My personal favorite, not easy, I couldn't do the whole routine the first six months I had it.
http://www.amazon.com/...654-0604020?v=glance I withdraw the yoga journal recomendation. They have a bunch of stuf by people I don't know on there right now. Search amazon for the names I listed.