I wanted to report a solved issue for the sake of the archive.
I own a DP43TF classic mainboard and I want to run 32 bit XP on it cos I own a license for that.
When the disks are in AHCI mode, the XP install gives STOP 0x0000007B. Inaccessible Boot Device.
When the disks are in IDE mode, install goes fine but the system resets spontaneously now and then.
I tried various things like swapping memory, check CPU temp and even insert more pasta between CPU and fan.
What resolved the issue was re-install of XP with use of the "Intel® Rapid Storage Technology" driver and the disks in AHCI mode.
Funny enough the F6 floppy method of installation didn't work for me ( I used an USB floppy drive). It keeps saying to insert the driver floppy after formatting the disk. . I created a streamlined Windows XP install CD with the driver incorperated. Install worked and spontaneous reset is gone.
Consider this before buying this board. XP is listed as "supported" but seen this experience there's a push to vista / windows 7.