Right click the task bar and uncheck "Lock the Taskbar". Then move your cursor onto the top edge of the bar until the arrow splits , and drag it up or down to the size you like. Relock the task bar then, if you like.
I would like for my gray taskbar in Windows XP to be single-spaced. Somehow it became double. I've tried right-clicking for menu options and nothing seems to work. Please advise.