Now I use a relatively-stable version of cranky old Windows Millennium, which of course doesn't allow you to defragment the hard disk unless you shut down all running programs (except Systray & Explorer - its not that miraculously stable!), which then prevents you from rebooting or shutting down normally, which leads to ScanDisk, and GAH! Therefore, I always boot into Safe Mode for my obsessive-compulsive disk defragmentation.
However, some time ago I noticed that my computer was refusing to boot into Safe Mode, no matter how deft my keyboarding skills at start-up. Thank fruck then that I had managed to force the boot menu (click Run from the Start menu, bring up the System Configuration Utility by typing msconfig, click Advanced on the General tab, check Enable Startup Menu, in Millennium at least), because my computer has just been REFUSING to LOAD up the DESKTOP without BSOD'ing loads, and then, when I turn the box off & on again and ScanDisk naturally kicks in due to improper startup, it was REFUSING to either COMPLETE it or to LET ME CANCEL, GODDAMMIT! And without Safe Mode coming to the rescue, the monitor before me would have a Starbuck-shaped fist in it.
So my previous lesson to you, dear friends, is this: check yer brakes before its too late. And clunk click every trip.