Disk chaching on SATA drives stops after reboot

Hello,

I have a ASUS motherboard P5 series (dual core)
with 3 SATA drives, after a reboot the first “system/boot” drive has its enhanced performance option disabled (devicemanager->diskdrives->ST300xxxx1->properties->policy->”enable enhanced performance” , when i re-enable it the disk is at least 4 time faster then without due to the cache function on the disk. Can anybody help me to find out why this is disabled in the device manager, maybe BIOS setting (if any) that are inhereted by Windows? , I have tried all resources on the internet , but nobody has the solution. i even tried to set the registry-key to read only for the system, but no luck.

I hope the question is understandable..

thanks for any help you guys/girls can give me.