How to Remove Grub from your Boot Sector(MBR) but keep the Partition Table

It's one really easy command, if you know what it is ;)
sudo dd if=/dev/zero of=/dev/XXX bs=446 count=1

That helps you to remove any boot sector from that device, e.g. sda. But make sure you've got a boot sector somewhere! I can recommed installing grub to a USB stick for backup purposes.