That beats the purpose. The ideea is to quickly format.
Removing the MBR would be fine and should be very fast comming from grub4dos. I'm mostly affraid that this will also remove the MBR from the USB drive that grub is booted from.
Could I trouble you for an example boot script?
Well, you can use a set of commands in the menu.lst, making sure that the booted USB device is first disk (hd0).
99.99% of the times (since you boot from it) the USB device will be (hd0).
If we also assume that you have at the most 2 or 3 harddisk-like devices on any machine (besides the booted from USB stick), that could be (without particular complexities) something *like*:
title Wipe all MBR's but not (hd0)
cat --hex --skip=440 --length=4 (hd0)0+1 | set sig=
if not "%sig%"=="77 7B 99 E4" echo Oh, oh, USB device is not drive (hd0) && pause && halt
partnew (hd1,0) 0 0 0
partnew (hd1,1) 0 0 0
partnew (hd1,2) 0 0 0
partnew (hd1,3) 0 0 0
partnew (hd2,0) 0 0 0
partnew (hd2,1) 0 0 0
partnew (hd2,2) 0 0 0
partnew (hd2,3) 0 0 0
partnew (hd3,0) 0 0 0
partnew (hd3,1) 0 0 0
partnew (hd3,2) 0 0 0
partnew (hd3,3) 0 0 0
Of course you need to use your own USB stick disk signature instead of "77 7B 99 E4", and of course instead of a series of partnew commands directly in the menu.lst, you could instead execute a separate grub4dos batch that could be more "flexible" than this simple approach (or provide more overwriting, like zeroing the whole MBR, etc.) .
The time needed should be measurable in seconds, not minutes