I've got a 4 Gigabyte flash drive that I'd like to make bootable. For right now, I need it to boot DOS or DS linux. I'd like to have it boot to grub or something similar so I can select either one.

You know you’ve got a serious PC problem when your computer refuses to get through even the first phase of startup properly. If you can't get into Windows or macOS at all, then your troubleshooting ...