laptop hard drive spin-down APM stuff - controllable??

[BSD baby]

Anyone who's using FreeBSD with a laptop:

I'm having problems with my hard drive spinning down (sleeping) every 30 seconds.

Is that something that's controllable in FreeBSD?   I don't see it in BIOS.
Is it a kernel thing?

This thing sleeps and wakes, sleeps and wakes about every 15 seconds.
Everything else is fine and it doesn't do it when I boot into Windows.

Thanks for any help!