I just got this fine aircraft, and after figuring out the engine start procedure, I've noticed that when I move the throttle when I'm on the ground, a loud alarm sounds.It stop the second I'm airborne.Any ideas?

This is usally moving the throttle above (about) 40% without flaps. Try taxiing with a light hand on the throttles.

What you hear is the "take-off configuration warning" which is triggered while incresing thrust towards the take-off range when any of the following conditions are true:-trailing edge flaps NOT in "flaps 1" through "flaps 15" range-leading edge flaps 1 and 4 not extended-spoilers/speedbrake lever not down-Stabilizer trim NOT in green band-parking brakes setthe warning stops once airborn. The only situation where you may hear the same warning in flight is when CABIN altitude exceeds 10,000ft which means that the cabin is losing pressure -or during climb not becoming pressurised proprerly! So, the "take-off configuration warning" NEVER SOUNDS IN FLIGHT. Unfortunately, even though it's easy to distinguish these two cases, there have been countless incidents in flight where the flight crew thought this was a take-off configuration warning. A recent example where the flight crew failed to interpret this warning as a cabin decompression was Helios flight ZU522 that crashed near Athens in 2005... BTW the "Cabin altitude warning" is not modelled in the current version of the PMDG 737, so keep an extra eye on that pressurization panel!! Chris Margaritopoulos kilo-mike-tango 737-800"only your mind travels you farther!"