NT 4.0 server Disk performance

Hello!

I have a problem that i've been mess'n with for a long time.. Under 98 my HDD disk tranfer performance is around 3.0 meg/sec uncached.. Under NT server 4.0 srvc pack 3.0 it's a pitiful .25-.5 meg/sec... now cached speed is much faster under NT, around 5 times faster, however the uncached is not anywhere near acceptable.. I have a Western digital 5.1 UDMA IDE hdd. I can't find an answer to this problem anyway.. anyone have any advice? Forgive me if this turns out to be a no brainer, but i'm quite new to NT...