Hi,
I have created a demo program running on Windows. This program does a simple N^2 force calculation between particles and integrates orbit of the particle system. After running the program, it show a performance result in Gflops (note I count 38 flops per one-force-evaluation, this may be different from other work).
http://galaxy.u-aizu.ac.jp/trac/note/wiki/Astronomical_Many_Body_Simulations_On_RV770#DemoProgram