Okay, geeks, put your geekdom to good use!
Windows 7. 3-year-old Dell laptop.
Mozilla Firefox froze while loading a web page. Okay. Ctrl+Alt+Del didn't work. Pushed the on-off button to force a shut down. Waited a while, turned the computer back on. Two loud beeps: it said "no bootable devices." I had it retry; nothing. Did the disk scan diagnostic thing; everything was successful except that the check for a hard drive failed. Afterwards, I tried turning the computer on and off a few times. Finally, got (forgot how) to a little screen asking, "Start Windows in safe mode?" Cavalierly said, "no, start Windows normally." The "Starting Windows" loadup screen came on ... and stayed there for 10 minutes.
Eventually turned the computer off manually again. Tried again and got the original can't find a disk message with the two loud beeps. (BTW my laptop's speakers are broken.)
Got Windows to start in safe mode. Backed up my hard drive, did a System Restore which made everything work good as ... well not good as new but good as it had been before. "Thanks, system restore!" I said gushingly. Shut the computer down.
Next morning ... bam, "No Bootable Devices." Diagnostic finds that there is no hard drive. Start Windows in Safe Mode again, here I am writing in this reply box.
Time to buy a new hard drive? Any other possibilities? My HD has only 100gb anyway, so I won't mourn the loss.