IBM ThinkPad & Phoenix BIOS

[GroundStatus]

Most old computers are donated to charities like Goodwill, sold on eBay, etc.

Electronics was a hobby that became my profession.  I ocassionally use old laptops for single
purpose projects.  The fact that they run slow doesn't matter.

I've got an IBM ThinkPad - Model T23.  It may be old, but it's in excellent condition.  (As you
probably know, IBM sold its PC division to Lenovo years ago.)

Specifications:

CPU: Pentium III - 1.20 GHz
RAM: 768 MB
BIOS Type: PhoenixBIOS 4.0 Release 6.0 for IBM ThinkPad
BIOS Version: 1.20 (1AET64WW)
BIOS Date: 10/18/06
Chipset: Intel 3575 rev 4

The attached image shows a typical ThinkPad.  A large open slot called an Ultrabay accepts a
Drive Caddy.  The Caddy is for a 2nd internal hard drive.  A floppy or optical drive can also be
installed in the Ultrabay.

This 2006 Phoenix BIOS is the last official update for the ThinkPad T23.  The project I have in
mind requires disabling or enabling one of the two internal hard drives.  Can I add this feature?
I've never modded a BIOS.  

I googled "replacement BIOS."  The first few listings were Coreboot and Libreboot created by the
Linux community.  Apparently, you can replace an old BIOS with these Linux creations.  My head
almost explodes when I read posts at Linux forums, because the technical lingo is completely
alien to a lifetime Windows user like me.

If I can't add "enable device" and "disable device" to the Phoenix BIOS, I might consider Coreboot
or Libreboot if they provide this option.