You have something seriously wrong the requirements on that Software are very low, check your drivers, settings and Heat.
Recommended Specs for V2 "2011"
Quad Core 3.0 GHz
4Gb Ram
2GB Vram
Full DirectX 11 Support (currently, DirectX 10 is not supported)
You should also Check for answers here as this is something most people on Tom's forum will never see.
http://prepar3d.com/forum-5/forum/prepar3d-application-support/hardware-specific-questions/
That software is pretty CPU dependent BTW so a GPU upgrade will make very little difference, Pushing a CPU overclock and Ram Speed will make a bigger impact or upgrading to a Intel I5 or better since you gain up to 25% or more on performance in Software like this.