A breakdown of the Windows Experience Index scores. As you can see, the graphics are what drags the score down, followed by the hard disk.
Graphical performance is hardly a surprise, but the hard disk deserves a couple of remarks - firstly the drivers may not be optimal, and secondly, this score is for a 5400 RPM 'SATA 2' notebook hard disk. Notebook performance always lags behind desktop performance, so this again is expected.