Thanks for the lead Behrens!
I immediately suspected my piece of crap Umax Astra 3400 USB scanner (should have kept the far superior SCSI 600S).
Then I went after my piece of crap Wacom USB tablet (will trade for mouse)
Finally, I started the trial, error, and reboot process of killing services (thought Win00 was supposed to be protected from bad processes - I never had to reboot NT4 like this.)
Oddly enough, what I've discovered is that if I simply kill the Print Spooler (C:\WINNT\system32\spoolsv.exe) and then start it right back up, Sandra will run fine from there on out. My spoolsv.exe file is unaltered from the CD original so I suspect that something else is the real cause and killing the spooler has the side effect of allowing the bad app to do what it needs to do. I'm sure it must have something to do with that lousy scanner or my stupid LJ6P driver that wipes out all USB ports whenever I print, but further diagnosis will take a while - many many reboots.