I want to start running again after 22 years of not. 39 y/o male... very athletic in HS, track and field etc., stopped running after knee injury and then fell in with the 'wrong' crowd, smoking cigs and other things. Gave up smoking 8 years ago now, and I want to start running again because I believe it's the only way I'll take off and keep off the weight I've gained since not smoking. Eight years ago I weighed 180, now 225 (5' 11').

My concerns are my knees, shins, and lower back (minor bulging disc, but no flareups for 3 months). What kinds of excercise/augmentation should I focus on to prepare these parts for the added stress? I'm already walking 20-30 minutes a day, taking the stairs for anything under 5 floors, and stretching at least a few minutes every day. My left knee does occasionally (one day a month?) rebel for no apparant reason, but I think it's my weight. One step will be fine and the next I get a sharp pain under the cap, then every step hurts for the next several hours. It's enough to cause me to limp.

Should I brace the funny knee, or just strengthen the supporting muscles? Brace the back injury? Any other ideas? Really want to make this work... thanks in advance!

Definitely brace or wrap the knee just as a preventative measure, even for walking. If your ultimate goal is to get (and KEEP weight off) cardio/running is a good start, but you really ought to add in some strength training as well. Nothing keeps the fat off like muscle, and as you get older it's more and more important to keep that lean muscle because it only gets harder to build.
To see how your knee handles running, start with short intervals of jogging between walking periods. 30 seconds to a minute of jogging every few minutes throughout the walk should give you a good gauge on how your body handles the stress. If anything hurts or aches exceptionally, then you may need to consider another course of action (at least for the time being). Starting slowly should give you an idea of where you're really at without causing injury or undue stress. In the mean time, take longer walks. 20-30 minutes is really the bare minimum. If you can carve out the time to do it, up it to 45-60 minutes. You'll get more significant fat and calorie burn even just at the walking pace. Are you going to a gym or are you exercising at home?

If I were you I would just stay with the walking. At your age and weight those aches and pains may get worse to the point that you won't want to walk.

I was a runner from age 17 until early thirties. Because of the very aches and pains you are talking about I switched from running to walking and have never regretted it. I'm 52 now. On days that it is just too hot to walk or is raining I do my Nordic Track ski machine.

I walk 30 to 40 minutes, sometimes up to 50 or 60 minutes, almost every single day, (only missed two days this year so far). I log my miles every day on an Excel spreadsheet and am at 369 miles this year so far.