Porteus

Can anyone tell me how to fix the Master Boot Record on my thumb drive they won't boot up anymore?

This really depends on what you are wanting to boot into. If it is Porteus then you can use a console and move into the thumb drives boot folder and run the Porteus installer again. This will install the boot loader and write to the MBR of the thumb drive.

brokenman wrote:This really depends on what you are wanting to boot into. If it is Porteus then you can use a console and move into the thumb drives boot folder and run the Porteus installer again. This will install the boot loader and write to the MBR of the thumb drive.

I already try to do that and when I boot it I just get a blank screen. I can format it and put files on the thumb drive but when I put Porteus on it I just get a blank screen.

You do as brokenman says; if it doesn't work then your pendrive is defect

I already try to do that and when I boot it I just get a blank screen.

which stage is it? can you reach syslinux boot menu? what's the last string you can see on the screen?

If you have been playing around with the UEFI it is also possible that a GUID has been written to the USB device. If this is the case then you can return the USB to normal like this:
parted /dev/sdx
mklabel msdos
quit

If you want to nuke the MBR you can use this command (replace sdX with the path of your usb device)
BE ABSOLUTELY SURE YOU TYPE THE USB DEVICE PATH OR YOU WILL NUKE YOUR HD's MBR
dd if=/dev/zero of=/dev/sdX bs=512 count=1

I don't know going on but now up to 3 thumb drive that don't work. Wish I had another computer to try them on.

@Jack
disconnect all usb-devices (exept mouse and keyboard)
1)Try another usb-port
2)Try to boot them with plop.(boot a porteus Live-CD,at the splashscreen select plop,
in plop select usb)...just a try..
EDIT:
Have you changed something in your bios?

I found what is wrong with my tnumb drives they were fotmat fat and fat32. How dumb I'm I not to know that.