My advice to you is to start slowly and ease into a healthy lifestyle. Working out twice a day sounds like major overkill. Plus, you'll be more likely to just quit if results don't come fast enough.
If you want to do 30-45 minutes of cardio every day, that's fine. But you should lift weights no more than five times a week. Furthermore, you should alternate which muscle groups you work each day. The reason for this is that muscles need time to heal (while they're healing is when they grow). You should definitely up your protein intake, especially after lifting (get a shake powder--I recommend Designer Protein).
If you're looking to lose fat, then you should reduce carbohydrates. It is simply amazing how many carbs people eat in a "normal" diet. Read the labels of the foods you're putting in your body--you'll be astounded. Just because something is low-fat doesn't make it healthy (quite the contrary). If you don't want to go "low carb" then check out something more reasonable like "The Zone" by Barry Sears, or just create your own diet.
Usually, overweight people have developed a resistance to insulin (a hormone secreted by the pancreas after carbohydrate consumption) Insulin allows sugar (all carbohydrates eaten [with the exception of dietary fiber] are broken down to sugar in the body) to enter your fat cells and get stored. By cutting down on the amount of carbohydrates you eat, you release less insulin, and your body is slowly able to lose its resistance. Also, cutting out some carbohydrates reduces the number of calories you eat (unless you replace them with fat and protein, which you should to a degree).
Incorporate unsaturated "healthy" fats into your diet--most people don't understand the need to do that. There are certain fats which your body MUST have to function correctly (they're called EFAs [Essential Fatty Acids] and they can only be found in certain food items--mainly cold-water fish like Salmon). If you're not eating a lot of fish I would suggest supplementing flax seed oil into your diet (you can just swallow a couple of spoonfuls or incorporate it into salad dressing or your protein shakes).
Just strive for a balance. kami covered the big things, so pay heed to those (especially the part about water... drink as much as you can).
If you need any more info, feel free to PM.
l2c