I'd run the hard drive manufacturer's diagnostic next. If you get an error there, the hard drive is failing and needs to be replaced.
To run the diags, download and burn the Ultimate Boot CD to CD. It has all the hard drive manufacturer's diagnostic utilities, (plus much more). Simply boot your computer from this CD and select the utility you want to run.
If you aren't sure who made the hard drive in your computer, use Seagate's Seatools as it will work with most any make of drive.
just to make sure I tried everything, this morning I tried:
Booting to last known configuration
Booting to Safe Mode
all of these resulted in the "Stop: C0000218 (Registry File Failure)"
I also tried the Ultimate Boot CD. It boots to it, but from there, I'm not certain what to try. I ran a drive diagnostic and it came back clean. I did see a post when I googled C0000218 that said they resolved it with UBCD "Registry Restore Wizard", but I didn't see that in the menu. I'll check again.
I also tried XPRecovery, but asked for Administrator Password and I don't know it (any suggestion for Admin Password?)
And last but not least, I tried XP Re-install, but stopped when it said: "Installing multiple OS on a single partition is not recommended".
I haven't done an XP re-install for awhile, but I don't remember this message.
As far as the password goes, VirtualDr's Acceptable Use Policy does not allow its members to assist anyone in the recovery of lost passwords. Due to the open, public nature of this forum, any assistance given to help circumvent security measures, even for legitimate purposes, would be available for unscrupulous individuals to use for illegitimate purposes. This is a risk that VirtualDr cannot take.
If you have a legitimate need to circumvent a password scheme, please contact the vendor for the software / hardware and request their assistance. E.g. Windows XP password recovery issues should be taken up with Microsoft, Phoenix BIOS password recovery issues should be taken up with Phoenix Technologies, Dell's "this system is protected by a password authenication system" should be taken up with Dell tech support, etc. ...