You don't appear to have a typical blank screen/flashing cursor problem but a grub4dos command shell prompt issue. i.e. it has booted to grub4dos but the menu.lst failed to run.
I suggest you try some grub4dos commands like help, root, find, geometry (hd0), map --status and report back what you see. Also check the BIOS boot options for USB booting. Please use the Forum to reply and not this Guestbook!