Black Icons

I got a machine Win 2k SP4 which is showing black icons on the start button, i.e, control panel, documents etc icons are all black. Even if you open a folder, the sub folders’ icons are all in black, they are not displayed in the normal yellow folder format. At first when the user was explaining the situation i thought it was a virus, so i performed a full scan with the latest definition of the antivirus, but no viruses were caught. The machine is performing perfectly, but the black icons are so irritating to the user, even to me, this is new.
Please i need help to solve these black things