On my windows xp,all my icons have an underline and when i click them once they open. how can i deactivate it?

go to control panel -> then go to folder options -> then in the bottom you ll see "click items as follows" -> there its selected the first "single click to open an item (point to select) -> u chould sellect "double click to open an item (single click to select) -> than just apply and ok... its easy isnt it? hope i helped!