Can't you just hook up the drive to your windows 7 pc? If you've got any kind of ide connection (even usb ones) it should work.
Otherwise, create a Windows 9x bootable floppy and just full format three times with the /u command.
Or if you've got any wiping software for win 9x, create two partitions (let's call them C and D).
First one, install to drive C and wipe disk D.
Next install windows dir and program files to disk D and wipe 'free space' on C. All that remains will be system files (>1MB)
Then recreate the one big C partition and retinal everything as you'd like.
Nobody's ever gonna find any e-mail to aunt May or any old pr0n any more 😉