Just FYI in case anyone else has encountered similar weirdness.
My WindowsXP Home system recently started taking 5 to 15 minutes, yes minutes, to bootup. It would just hang with a black screen while it did its nails or something, then eventually start up.

I narrowed it down to a new SanDisk USB 2.0 model SDDR-91 CompactFlash reader.
If I unplug that everything is fine, or if there's a memory card in it again it's OK. But leaving it plugged into the USB w/o a memory card in it and it's snooze time.

The www.sandisk.com site recommended disabling "legacy USB support" in the BIOS and the Microsoft site's "Q282195" says that option isn't needed for XP systems. So I disabled that but no difference.