What you really want is not bootgui=0, set that back to 1.
If you see a line that says Bootmenu=0, change this to BootMenu=1, otherwise add the line Bootmenu=1 (right above the bootgui line).
This will make a menu of whether you want windows, DOS, safe mode, safe mode with networking, or whatever for up to 30 seconds every time you boot.
You can change how long the menu lasts if you don't hit anything by adding BootMenuDelay=<number of seconds>