*Also asked in - and replied to - the WinMe.General NG.*

The simplest answer is to boot - using the WinMe (floppy) Startup disk - and
at the A:\> prompt, type " format c: "  (no quotes and notice the colon
after the letter c)

That should format the C: drive.

However, if you want a more detailed instructions, a couple of very useful
documents are on your WinMe CD (and probably on your C: drive too) called
setup.txt file and cleanhd.txt which are well worth reading. You should also
and print out and have handy a copy of the cleanhd.txt file - a copy of
which you can also see here :-
"Windows Millennium Edition Cleanhd.txt File Contents"
http://support.microsoft.com/kb/271673/en-us

Also, be sure that you've still got a copy of the 25 digit product key,
before you start and any 'machine specific' drivers (often on a separate CD)
which *may* have come with your PC. (Don't worry too much if you haven't any
drivers as there's usually some work-around available)

Mart