Well, looks like it's my turn for some Windows XP troubleshooting.
My father called me up today to let me know that Windows can't log on. While loading personal settings, a dialog box comes up and indicates there was an issue with LSASS.EXE and that the system will shutdown. While it reminds me of the old Sasser bug from many years ago, the system is running Service Pack 3 (and I believe all updates as of two weeks ago), and also have Microsoft Security Essentials. They are also behind a router/firewall.
Booting into Safe Mode just gives a black screen with "Safe Mode" on all four corners, and does not bring up a login screen at all. Last Known Good configuration also doesn't work (though I think if the system gets to the logon screen, it considers that "good."
I'm heading over there tomorrow with some boot discs with malware/spyware scanners and such. Anyone know of something in particular i should look for and/or check?