Being below the Windows XP machine in the benchmark does not mean that your machine has poor performance. Some algorithms cannot take advantage of multi-core processors, while others can run on the GPU. You might have a different graphics card than the Windows XP machine, or maybe you were running other programs at the same time and less memory was available to MATLAB as a consequence. The benchmark is only informative.
As for code performance, there are techniques you can apply to speed up processing. They are listed here:
