I've got an USB pen drive and I'd like to turn it into a bootable MBR device. However, at some point in its history, that device had a GPT on it, and I can't seem to get rid of that. Even after I ran mklabel dos in parted, grub-install still complains aboutAttempting to install GRUB to a disk with multiple partition labels.  This is not supported yet..I don't want to preserve any data. I only want to clear all traces of the previous GTP, preferably using some mechanism which works faster than a dd if=/dev/zero of= to zero out the whole drive. I'd prefer a termina-based (command line or curses) approach, but some common and free graphical tool would be fine as well.
Remove all traces of GPT disk label
partition;disk;gpt;parted;mbr
If you don't want to fiddle with dd, gdisk can do:$ sudo gdisk /dev/sdbGPT fdisk (gdisk) version 0.8.8Partition table scan:  MBR: protective  BSD: not present  APM: not present  GPT: presentFound valid GPT with protective MBR; using GPT.Command (? for help): ?b   back up GPT data to a file<snip>w   write table to disk and exitx   extra functionality (experts only)?   print this menuCommand (? for help): xExpert command (? for help): ?a   set attributes<snip>w   write table to disk and exitz   zap (destroy) GPT data structures and exit?   print this menuExpert command (? for help): zAbout to wipe out GPT on /dev/sdb. Proceed? (Y/N): YGPT data structures destroyed! You may now partition the disk using fdisk orother utilities.Blank out MBR? (Y/N): YVerify:$ sudo gdisk /dev/sdbGPT fdisk (gdisk) version 0.8.8Partition table scan:  MBR: not present  BSD: not present  APM: not present  GPT: not presentCreating new GPT entries.Command (? for help): 