How to prevent HDD spin-down.

[J.B.]

Hey. I purchased a new WD laptop hard disk drive, but it keeps spinning 
down and parking its heads after 25 seconds of inactivity. How can I 
disable that feature or extend the timeout to something less idiotic? I 
checked the BIOS, but there's no setting for it. I booted into a Linux 
(Debian-based) OS duel-booting on the same disk, and the disk doesn't 
spin down, so either Linux is doing something to override that feature, 
or FreeBSD is doing something to enable it (possibly a package I 
installed). Thanks.