Can't remember what my HDD score was before I upgraded but I get
7.8.

Apparently topping out at 7.9 on the HDD rating is pretty hard to do but not impossible.
My CPU/RAM (Intel i7 870 / 8GB 1600Mhz) is holding my overall rating back at 7.5 and I get a top score of 7.9 on the 3D/desktop graphics thanks to my ATi HD6950.
I take the Windows Experience Index with a grain of salt though. It's more a quick general information on how well your computer performs more than anything.