[SOLVED] Need to delete GRUB in MBR

I am trying to clean up a multi-boot.
I have 4 OS’es;
sda1 Kubuntu 14.04
sdc1 Ubuntu 12.04
sdc5 Kubuntu 12.04
sdc6 Xubuntu 14.04

I need to reinstall (or do something) Ubuntu 12.04 on sdc1 as there is a problem with the GFX driver, the screen is just showing dark areas where the icons are (see screenshot). I have installed it several times and still get the same result.
I know I have to change the GFX driver but can’t do it if all I see is blocky graphics.

I installed the grub in the MBR of sdc and it keeps booting to sdc5 Kubuntu 12.04 but I want to stop that so I can get back to the grub where I have a choice of OS’es to boot to. I have Googled removing grub from MBR but all I keep getting is results to put Window$ boot back on. I just want to delete grub from MBR.

I am also going to remove Xubuntu 14.04 from sdc6 and replace it with Ubuntu 14.04.
Why is it that when installing an OS there is no option to NOT install a grub to cater fro people with multi-boot systems?

Anyone have any ideas?

If you do what the title said then you would not be able to boot into anything.
Though if that is what you really want then do it with (at your risk):
Assuming it is /dev/sda the current first boot drive containing the grub.

sudo dd if=/dev/zero of=/dev/sda count=1 bs=446

On the other hand if you just want to repair the grub then need to define/clarify few things:
a) which disk is the first boot drive in the bios
b) which distro you want to designate to be the master boot controller

Once you got that info then come back here.

so you have sdc set as the first boot device in the BIOS ?

Looks like it’s fixed itself, I realised I didn’t want Ubuntu 12.04 but Ubuntu 14.04 so I installed it over 12.04 and its booting OK now.