Plextor question.

I have a Plextor 16/10/40 drive and I noticed it spins endlessly when there
is a disk inside. I assume that the drive was set this way so there would be
no delays for spin-up time. But I would rather not have the drive spin needlessly
for hours on end if I'm not accessing a disk.

I was wondering if one of you guys might know where to set the drive to
spin-down when not in active use for a certain length of time. I'm not
sure where that setting would be. I'm using 98SE. Thanks for any info.