I just installed 12.04 LTS onto my Acer Aspire One from a USB thumbdrive, and I cannot reboot unless I boot from the USB drive. If I have the USB drive plugged in, it boots, and it looks like the system is running of the HDD (/ is mounted from there, the USB drive is /media/PENDRIVE, everything works fine when I unmount it, etc).
If I reboot with no USB drive mounted, I just get a flashing cursor. It looks like a misconfigured boot loader. The Terminal tells me that grub is not installed ... so just how does Ubuntu boot these days, and how can I make the HDD bootable?