So I'm building an htpc, and was going to get a recommended slimline from HP. then realized that there were no HDD bays for expansion makes sense with a tiny PC. so looking at the other series (m, d, a), i realized i couldn't tell how many slots they contained for expansion. not even on hp's website could i figure it out (other than at least two, since a harddrive option when purchasing is 2x750gb drives). anyone know the expansion slots available on these models (m, d, a)?