WinXP Pro won't start: lsass.exe and MPR.dll

I'm trying to get a friend's system back up and running. System specs are:
AMD 750 Duron
WinXP Pro running on NTFS
128MB PC100 RAM
40GB HDD
52x CD-ROM
3.5" FDD

The problem:
On starting, the WinXP "loading..." screen appears, and is replaced by an error message showing the following in the title bar:

"lsass.exe - Unable to locate component"

In the dialogue box appears the message:

"This application has failed to start because MPR.dll was
not found. Re-installing the application may fix the
problem."

Clicking on "OK" results in a dark screen showing only the mouse cursor, and no hard drive activity. The cursor responds to movement of the mouse, but nothing else happens.

Possible diagnosis:
A virus or worm infection that has corrupted MPR.dll.

Steps taken so far:

Not much. I have very few tools capable of dealing with an NTFS-formatted hard drive. And I have very little experience with maintenance of a WinXP system. About all I've accomplished so far is to establish that the hard drive is accessible and does not appear to be corrupted.

My problem:
I can't use the PC-cillin emergency disks I have to start the system to run a virus scan because those were built on a FAT32 system. Any other tools I would use to run a virus scan require that the system be able to boot from its own hard drive.

It seems that maybe I could get the system running if I could replace MPR.dll with a good copy. My wife has a system that is also running on WinXP Pro, and there is a copy of MPR.dll on her system. But that system also has a FAT32 format, so I can't build a startup disk on her system that will handle an NTFS hard drive.

"Re-format and re-install" is an answer that has been offered more than once. But he has no current backups. He's not happy about losing his data files, and it would be nice not to have to re-install all the software.

So:
How do I run a virus scan?
How do I get MPR.dll onto my friend's system so I can run a scan?

 

Sounds more like the sasser virus to me! Visit this link to see if you are infected, and what to do if you are!