Another one needing help formatting

[joebmc]

I got a problem,

Im running win xp pro and want to do a clean install so i need to format my hard drive (wd 80gb),
I put a start up disk in my pc when i turn it on (which i got from creating in win ME) and when i get to the dos prompt type "format c:" as i've been told before, but i then get the message along the lines of "cant format c:, drive not available" or somthing like that!

Any help would be nice

[Barry]

just boot from CD and use the format option when you're installing