kernel panic on SATA drive

[Edward Sanford Sutton, III]

The FreeBSD Developers' Handbook describes how to get panic information (and 
dig out further details). 
http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug.html#KERNELDEBUG-OBTAIN
Was there any output before "ad7: FAILURE - device detached"? Losing the drive 
in the bios makes me think hardware, but I'd check for any firmware 
problems/updates if they exist.
I have not tried yet, but FreeBSD8 is supposed to finally handle the anxiety 
of losing a drive. 
http://freebsdfoundation.org/press/2008Dec-newsletter.shtml#Project1

I would try smartctl from ports; run a long scan and read the full output to 
see if it passes or if you get a response like:
# 1  Extended offline    Completed: read failure       20%     32490         
308342849
Also look above that output to see if there any metioned 'Error ## occured at 
disk power-on lifetime' type of messages.
to scan, run:
smartctl -t long /dev/ad7
after the scan, read output with:
smartctl -a long /dev/ad7

What motherboard is it? "GeForce 8200" sounds like a graphics chipset to me.

For hardware analysis, try to isolate it to a particular drive (sounds like it 
is only the seagate), cable (data or power), motherboard sata port. When the 
drive is not recognized, does a coldboot redetect it? Does the drive start 
any audible clicking? What model of drive is it? Make sure the drive is 
dusted off, increase the cooling, and try again; I have a drive that flakes 
out if the three speed antec fan in front of it is only on low but stabilizes 
when kept cooler; its a great hint to me that the drive is near life's end.