4x1 gig Geil running in sinngle channel

[YabbyU]

I just finished my build last week:

E8400
EVGA 780i
9800GTX
4x1 Geil DDR2800
xp home
coolermaster 1000w
antec900

my memory, according to CPUz, is running in single channel. XP is showing all 4gigs there, 2.5 something available....

Any ideas why it would be running in single channel?

Thanks