I recently had a very similar problem where I needed to format and was only able to start up in safe mode, where it is impossible to reformat from as I was already running windows on the same volume. The only way I managed to get around this, after many agonising hours as I have no a: drive to insert a boot disk, was to insert a Windows XP setup CD and press F8 as it reached the initial boot screen. There was then an option somewhere on this menu that mentioned something about booting using the CD drive (sorry I cant be more specific, but I believe there is only one like this anyway). This option never worked instantly for me, but pressing F1 afterwards to retry always did strangely enough. Now after the windows setup has initiated, you'll want to select the option where it says about restoring a previous windows installation and NOT reinstalling windows. This will then chuck you out into a command prompt where you will be able to reformat the drive.
Hope this helps.
