The icons next to the clock are not appearing on the taskbar

Hi! Currently I am using Windows XP Professional OS on my computer. Some days ago, I formatted my computer and then I noticed that the icons next to the clock are not appearing. The only thing I could see on the taskbar is the clock. I got one solution and set the priority programs on the startup items accordingly but the problem still exists. Is there any way to fix it? Looking forward for your kind cooperation. Thank you.
