I know most everyone makes a big deal about the "fat burning" cardio, but I also know that having a high % of lean muscle bumps up the metabolism, and burns fat faster. If you're working out hard with the weights, you are getting the old heart pumping too.
What would be a good regimen for someone who used to be a "hardbody" but has become soft due to inactivity?

Well its good to do both.. I would workout and then run... but when you get to your right size where ever you want to be... u could run once a week

Well the truth is that you have to find a balance. If your looking to get in shape quickly id start every session with a small 10-20 minute run to get warmed up and then hit all your usual weights. Also don't forget to give your body the rest and vitamins it needs.

Is high protein diet need for weight traing

If you used to be a hardbody, then get lifting weights and you'll find muscle memory will help get the body back again. Concentrate on compound exercises using free weights, particularly squat, deadlift and bench press.

When you are doing cardio, work hard. The "fat burning zone" is a myth, based on playing tricks with numbers. Expect to pant and sweat to get results.

Clean up your diet, cut out the junk food, soda and white carbs.

Cartea, you don't need to have huge amounts of protein to lift weights, but you'll get the best results if you have enough protein. 1g of protein per pound of lean mass is a good starting point.