Additional odd behavior: machine can no longer write to floppy disk. A: drive appears in My Computer, reads disks, boots from floppy, formats floppy, but will not write to floppy -- freezes solid if you try. On freeze, nothing works but hard shutdown with power button. Drive replaced with new unit, behavior exactly same. Tried Partition Magic boot disks and got "Error #91: Disk Manager has been detected on drive 0, but Disk Manager is not running. If you are booting from a floppy, remove the floppy disk and reboot. Press and hold the key as your computer restarts. When prompted insert your boot floppy and continue booting." and "Error #87 Unable to initialize the engine" Those directions don't work but does the Disk Manager error mean that something is screwy with the system? Also found that booting from a 98 boot disk I could copy Ntldr to the floppy drive (apparently in spite of "Invalid drive specification" error, at least dir showed file) but not Ntdetect.com or boot.ini. C: & D: are NTFS volumes. Computer did not lock up attempting to write to floppy in DOS.
This question has morphed into something else, so I am going to change the techpoints and thanks for the help!