I just recently started the C25K program, completed W1 just fine, W2D1 I had really tight shin/calf on my right leg at the beginning of the workout and by the end of it was experiencing some pretty good knee pain....I've never had knee pain before so I don't really have a good way of classifying its intensity, but every step was say a 3 or 4 on a 1-10 scale of pain. I ran through it anyway and completed the workout. Next day, knees very sore walking down stairs in particular, could feel small amount of pain even walking. Did not exercise that day in hopes of resting. Yesterday I bought new sneakers since my old ones were very worn out and the pain wasn't as bad as the first day, but still there, and once again this morning my knees are very sore walking down stairs and a little sore walking up stairs. So....my questions are 1) is the knee pain the result of the bad sneakers + tight shin/calf on the first day, or is this a sign of a more chronic problem, 2) should I rest until there is absolutely no pain or just rest a day or so and then run through a little bit of pain again, 3) should I see a doctor and/or get a knee brace at this point or wait until ??? I've never experienced any kind of joint pain in my life so I'm at a loss as to how concerned I should be. I should mention that I'm only 26 but I'm overweight so certainly I'm putting a lot of stress on my knees when I'm running, but I'm very excited about this program and don't want to have to stop. Oh, and I've run in the past few years up to a mile at a time (once in awhile, my motivation tends to ebb and flow) with no joint pain at all.

Many thanks for any advice!