is there still a way that you can start up an operating system, from pressing spacebar on an external keyboard.
i have a dell vista laptop and a dell external usb keyboard, rather than have to open the lid each time on the laptop to start up, i would like to start it up from the keyboard in some way

Some BIOS have this option. Some do not.

You'd have to check your manual or browse your BIOS Setup and look for such an option. Probably under Power Management.