Problem with some addons

I have a Athlon 3200 64b with 2gDDR400 Kingston, video card x800gto 256 agp, 2 hard disk (sata 37g 10000rpm where FS are instaled) and a old philips sound card.When i use some airplanes like B200 Aeroworx, 737 PMDG, 707 Captainsim and others the FS came freeze for a minute and when i change the view (vc to external view) happend the same problem.I have installed de expansion for FS9, the last FSuipc, the Omega drives for my video card, directx 9.0c and the last drivers 4-1 via agp.If somebody have an idea that what cause the problem PLEASE HEEEELP