upgrading GPU on my DELL XPS420, would it fit it?

hi guys,
i recently got a dell xps 420 from someone. it has all the basic setting for xps 420.

q6600
3gb ram
320gb hdd
ati 128mb 2400 pro

everything, i like.. but the graphic card have to be changed becasue of my game play.
im not a high end graphic card user. all i play is world of warcraft,
and i get about 20-30 fps with moderate setting.

i figured out that this xps420's power supply is good enough to hold geforce 8800 gts(g92) and
i believe it has plenty space for that card.
my question is,
isn't 8800 gts goes into the pci express 2.0 x16 slot?
but im not sure this motherboard has one.

does anyone know?
if i do have one slot, then i am happy, if i dont,
what could be my another option for the gpu upgrade?

It should be a drop in replacement. I doubt you'll have any trouble at all.