Finally, left with no choice, I risked it, and now it is okay again... but not directly. Let me describe my steps for anyone that finds this post searching for help in the future:
Booted into the command line "Rescue Mode" from the XP cd, selected my Windows installation and entered my admin password as usual to get to the prompt... "C:\Windows".
Days before, I tried "fixboot c:", but it didn't help. But I didn't realize at the time you MUST be in the ROOT of C:\ before executing any boot commands.
My steps:
CD \
fixboot c:
exit (reboot to see if that fixed it. No)
Back into Rescue Mode:
cd \
fixmbr c:
(no feedback on screen. Just returned to the C:\ prompt)
fixmbr (with no drive specified)
(feedback with warning about possibly destroying partitions. Deep breath. Yes. Response: "fixed".)
exit (reboot)
(fixed, but now I was being prompted to select my OS at boot: (blank), Win XP, (my Admin password) and Win XP Pro. Selecting either Win XP option started Windows normally. All my data on all partitions was there and intact.)
(Try to fix the issue of now being unnecisarilly prompted to select an OS. Reboot from cd into Rescue Mode.)
cd \
bootcfg /rebuild
(resonse, done.)
exit (reboot)
OS selection still there. Go ito Windows. Right-click My Computer. Advanced tab. Click Settings under Startup and Recovery. Click Edit button under "System Startup" section. This opens "boot.ini" in Notepad. Saved a copy with Save As. Reboot Windows w/o making changes (this is because "Save As" changed the path "boot.ini" will save to).
Same thing, open "boot.ini" for edit. Deleted the extra OS choices (leaving just XP Pro with the "/fastdetect" switch)
Save. Close. Reboot. Fixed!
Thank you. Thank you. No applause please!
>> Stay informed about: Okay to use FIXMBR on drive with multiple partitions?