I have to admit some confusion. Is "IDE" a general term that covers both SATA and PATA? In any case, I believe this setting tells the system to use a generic AHCI to the SATA devices. (My BIOS has a bunch of IDE config options but nothing ever mentions SATA.)

Here:

http://linuxmafia.com/faq/Hardware/sata.html

they suggest that you should only activate AHCI long enough to install the proper drivers to get native device support...and then switch it back.

Note that the installation proceeds without difficulty off of the SATA DVD with the "legacy" setting selected.

But as for the immediate concerns, this isn't top of the list. The motherboard thinks the cpu is running at 1 degree C and rebooted about 10 times at one point, though it seems to have settled down now. Nevertheless, I'm kind of nervous...

And for some reason the mouse isn't recognized. Onward...onward...

Given the errors I suspect failing hardware. Check all connections are properly inserted and in the correct connectors

IDE is another name for ATA(PI), now refered to as PATA. SATA uses SCSI-style drivers and are thus recognised as sd* devices, where IDE/PATA are in the hd* range.

SATA mischief with Debian?

Try this link (It's a l-o-n-g thread and (k)ubuntu orientated - which is derived from Debian, so will probably apply, read it ALL) but it worked for me.

http://ubuntuforums.org/showthread.php?t=415009&page=14

Hope this helps.