Nvidia GeForce 9400GT woes.

Been a while since I last was commenting here. And,unfortunately,as I return,I come to you all with a problem. I have a Dell Dimension 2400 with a Pentium 4,at 2.8 gHz. I have 2 gig ram. I bought and installed a GeForce 9400 GT vid card in my system. It has a gig of on board memory.My last card only had something like 128meg memory on it. Yet,it did far better than my newest card. It is a PCI card and NOT PCIexpress.With the new card of 1 gig memory I would have thought it would let me place my FS9 settings to max across the board and look great. Fact is,my older card did a better job. When I am in SPOT mode and circle around he craft,it does the hesitating jumping view like my frame rate went down to 2 per sec. What is the problem? I am not great at setting vid card settings with the program that comes with the cards,like setting vertical sync and such.Not sure what all that stuff does.All I want is to smooth out my frame rate.Get a smooth running sim with all settings maxed out (FS9). Any computer jocks out there that can give me a hand here? Thanks folks.