After the boot process, a quick look using the bundled System Monitor tool reveals 100% CPU utilization, and a tremendous (Megabytes) amount of file system Dirty Data, for an inordinate period of time. Again, just a guess . . .
During the boot, I cannot hear the usual disk drive seeking going on. The drive light comes on, yet there are lengthy pauses interspersed between audible cues from the disk drive that something is happening; the dive just sits there for minutes on end. A little activity, then a big wait (several minutes), then a little more activity (maybe a second or so), then a big wait, on and on through the boot process.
I realize this isn't the fastest PC on the planet anymore. The 1 hour 45 minute time required to boot the machine is what leads me to believe some task is railing the CPU and preventing the rest of the processes from getting any CPU time.
Worth noting is that once the boot process is complete, things seem return to normal. As I'm typing this (and browsing) the operational parameters appear as expected. Even CPU intensive apps such as Winamp run fine.
What used to be a three minute boot process now takes almost two hours; the machine appears locked, but eventually, if given enough time, completes the process. I'm stumped . . .