BTX Halted - not such a newbie question

[Joy]

I'm having problems installing FreeBSD V6.0 on an HP (ne Compaq) desktop PC.
The install appears to go fine from CD, or via FTP, but on rebooting the
installed boot loader halts with a register dump and "BTX halted" error
message. So no rotating curser, no kernel messages just the dump and error
message.

Now I've been using FreeBSD for years, so immediately think "Disc Geometry
problems - enable / disable DMA" etc. Nope, I've tried the various BIOS
settings and manually setting the geometry in fdisk. I've also tried changing
the boot manager for a dedicated MBR.

Here are the BIOS settings I have tried:

      Transfer Mode: Max UDMA, Ultra DMA 0, Enhanced DMA, Max PIO, PIO 0
      Translation Mode: Bit Shift, LBA Assisted and User Defined [1023/240/63]

Here is the spec of my machine:

Spec: Compaq Workstation xw6000
Proc: P4 2.8GHz
RAM:  1024MB
HD:   80.0GB, Maxtor 6Y080L0 (Primary IDE master)
Most onboard devices (USB, Serial, etc) have been disabled.

Any help appreciated 

Joy
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