As none of the 'big guns' have replied yet, I'd start with some squats, some situps, some consistent-paced jogging with an MP3 player, get a decent skipping rope and try to keep a consistent comfortable pace... can be done anytime for 5 minutes.. And ride the bike!

If you can't do skipping for 5 minutes, take a break when you've had it, stop the clock, and carry on until you've done 5 in total, but with anything, try *not* to stop. Even if you're just jogging on the spot, it all helps.

Then as it gets easier, up the pace, and try jogging 30 seconds, then sprinting 30 seconds, and so on. Same with the skipping, with everything.

Learn some basic stretches which'll help with cramps/strains if you're not used to it. Time yourself on a mile run, then time yourself every two weeks. If you do it day to day, I've just found it winds you up!

Eat properly, go for the low fat options, cut out crap where you can, and if you drop weight whilst increasing your cardio fitness, you're approaching the problem from two angles!

Good Luck!