I got my repaired computer back from the shop with a new Intel Desktop board DQ965GF w. Core2 Duo CPU and 4GB DRAM, plus an nVidia GeForce 9600 video board w. 1GB.
XP PRO Service Pack 3 was installed w. Norton Internet Security and Norton Ghost, plus one reformatted Western Digital drive and one blank reformatted WD drive.
I cloned drive C:\ to the blank drive and rebooted. This seemed to confuse the computer, which had trouble completing boot-up. I disconnected the second drive and proceeded for several weeks, creating Ghost Restore Points every few days, but the PC had trouble completing boot-up, often failing to Blue Screen.
Eventually I went to the Restore Point right after I removed the second drive, but still had trouble booting. During the process, I added four external USB drives and Adobe Lightroom 2.0 and Photoshop CS3.
Several days ago, the boot-up trouble went away, but the computer began turning off from 10 minutes to an hour after being turned on.
Otherwise, everything seems fine.
I will attach a HiJackThis log but first I want to get this message sent before the system shuts off again ...