everyone, i need some help with this system.

I bought this board 2nd a while ago and it was tested ok.
the setup is,

OS drive 320GB 3200AAKS WD caviar blue
Data drives WD GP 1TB x2
rams team xtreem 1066mhz 2x1gb
psu corsair vx550w
dvdrw lite-on cant remember model number.

OS Windows XP SP2.
ati drivers 9.2


for some reason the system is incredibly sluggish in operations. opening a movie file seems slower than my ibm laptop.
opening a folder within the data drives takes ages to complete.
task mgr does not show any resource hog.

the bios' sata config sets the drives at IDE.
AHCI and RAID does not allow the system to boot normally. just says error loading OS for AHCI.

i didnt install the raid drivers or intel matrix storage though.

HD tune results