can a Asus P5K deluxe mobo run 4 gigs

[dubs89]

My problem is i have a really nice computer but it is horrably slow I may think it has something to do with the RAM because vista says that i am constantly using 50% of it.. so here is a short list on the hardware/software i have:

-Vista home premium 64bit
-Asus P5K deluxe/wifi-ap atx LGA775 P35 DDr2 1333fsb mobo
-(2x) corsair XMS2 TWIN2x2048-6400C4 2GB 2x1GB PC-6400 DDR2-800 CL 4-4-4-12 240pIN dual channel memory
-western digital raptor SATA 10krpm 150GB (Vista is installed on this drive)
-I am also running 2 24 inch monitors
-intell core 2 quad Q6600 Quade Core Prossesor LGA775 kenstsfield 2.40GHZ 1066 FSB 8MB
-Nvidia Quadro FX by PNY FX 3500 PCI-E 256 MB 256BUT DDR3 Dual DVu Video card
-hitachi desksttar t7k500 320 GB sata 7200 RPM 16 MB (In stalled in a external hardrive with e-sata and usb)

Please help me out i am very confused as to why my computer so running so slow any suggestions? does anyone think my ram isnt working the the mother board?

 

[Vizy]

your mobo supports 8gb

 

[dubs89]

but in all four slots? 1 gb per slot? i read that most mobos wont read more than 2 slots... any other ideas as to why my comp runs ass slow in programs such as adobe illistator in design and photo shop? and when i delet a item off my desk top it doesnt disapear for like 10 min.

 

[The Linguist]

I've got the p5kc and I've got four 1gb sticks and it runs no problem.