I got a 2.0 in my first semester of physics. It was a summer course, I got married that summer, and I worked full time. Every premed authority I have asked told me it will not be a big deal, just be prepared to justify to adcoms or interviewers why you slacked at that time. Also, be sure it is a rare occurrance. 1 or 2 C=OK if there is a reason, more than that=greatly decreased chances. One more thing, make sure you do not get a steady decline in grades. It is better to get A's and B's, and have a C or 2 thrown in then to get all A's, then all B's, then mostly C's.