Adding another hard drive

[Rich Demanowski]

I'm trying to add another hard drive into my system, a 250GB Western 
Digital 7200RPM SATA drive, and when I have it plugged into the 
motherboard the system hangs when it gets to:
    Timecounter "TSC" frequency 1803775604 Hz quality 800
    Timecounters tick every 1.000 msec
    acd0: CDRW <LITE-ON COMBO SOHC-4836K/SPJ2> at ata1-master UDMA33
    ad4: 114473MB <Seagate ST3120213AS 3.AHH> at ata2-master SATA150

Normally, I see the following line right after that:
    Trying to mount root from ufs:/dev/ad4s1a

and then the mount messages, the daemon starting messages, and the login 
prompt.

When I have the new hard drive plugged into a free SATA port on the 
motherboard, it hangs the system hard, I have to unplug the box from the 
wall to shut it down.

The BIOS sees that drive just fine.

If I unplug it from the SATA port on the motherboard, the system starts 
up just fine again.