Got a gig of hard disk space to spare? Here's a good safety dodge that (bizarrely) I had to use within a week of doing it. Basically it consists of making an exact copy of your \WINDOWS directory under another name.
I used XXCOPY (which is a kind of super-Xcopy [command-line 32 bit Windows program] available from
http://www.xxcopy.com/index.html ) to clone my \WINDOWS folder to \WINCOPY
Syntax: XXCOPY C
WINDOWS C
WINCOPY /CLONE [add /PB of you want a pretty window with a progress bar]
Plain OLD XCOPY won't do - it's too slow, chokes on your swapfile and files with bizarre attributes and is generally unsat.
If your Micro$oft Wonder ever goes Tango Uniform you can boot with the emergency disk, rename \WINDOWS to \OLDWIN and \XWINCOPY to \WINDOWS and reboot. Just remember to update your \XWINCOPY regularly and only when the system is behaving smoothly.
If you're truly paranoid (like me) store another clone on a removable hard drive and keep that in the woodshed (actually I clone the entire drive...). Just cloning C
WINDOWS probably won't work properly in ME (ugh!) or eXPensive or 2000 though.