I have just bought PMDG 737 800/900 I have xp on my system and installed the following.flight sim 2004 the fs4 update the PMDG softwareI have been useing it quite a bit but am unable to worok out werther the following is a problem with the software or somthing I am doing wrong/misunderstanding.when I atempt to trim the elevators I here a sound but the trim moves in an iratic way no matter what I do.I did the following to prove the problem out.canceled all key and joystick assingments to the trim and then created new ones.checked the autopilot was offthe trim works fine in any other aircraft I select, any one offer me any clues on this?

Ra,when you say iratic - what exactly do you mean? When I trim, the needle on the throttle quadrant moves as it's supposed to, as does the aircraft. This is under manual flying - yes? Do you have a registered copy of FSUIPC? and if so, do you have any assignments in there that may need adjusting?

not sure about the FSUIPC thing , I bought the product on cdrom.what happens when is this.in the aircraft under manual flying I hit the buton for trim down.I get the following , some kinf of sound sampe playing, the trim wheel in moving but is moving a bit one way then another, this indcator will move a bit then will return to the middle of the green section, it is as if somethinf is overwriting the comands I am puting in, I wondered if there was somthing I was missing as this will all work fine with other aircraft. as I said i notices there is an FSUIPC menue but I have not touched any of that stuff.