The unsupported format message was from the monitor and not the pc
I guess you're talking about the grub menu. You can edit /etc/default/grub to try to get it sorted; you need root permissions for this (so use of sudo or gksudo). Find the following line in that file and remove the '#' at the beginning.
Save the file and run the below command (this will update grub.cfg)
Next time you boot, you should get a normal grub menu (in case you're dual booting).
If you're not dual booting (and I think you're not), you can force Grub to show the menu. The same file contains a line like
Remove the number at the end and save the file (leave the '='). Next run update_grub as shown above.