[ubuntu] No GRUB after ubuntu 12.04 64bit install

Hi,

I just got a new fujitsu lifebook with a pre-installed win7. I tried to install Ubuntu 12.04 desktop amd64 with a live usb stick and after install I don't get a GRUB menu to select to start Ubuntu.
Am I missing something here?

I also can't start the laptop with my external HD plugged in...

Thanks in advance