I'm running XP
And this morning when I booted up, I got this message:
Primary Master Disk HDD S.M.A.R.T Capability Disabled. Replace Disk and then press any key.
So I checked around and discovered I had left a floppy in the drive. I removed it, hit a key and my computer kbooted normally.
Why did the floppy get called the master disk? I know computers are often set to check the floppy drive or the CDROM to see if they should boot from it, but master disk meant the hard drive itself to me. S.M.A.R.T means "Self Monitoring Analysis Reporting Technology" (Hard Drive Feature - Warns of problems before total failure.")