If the computer is a laptop, it may have a built-in Infrared port. This basically emulates a serial connection over an Infrared link and requires a direct line of sight between the Ir ports in the two devices.
<<< In that four options are there.. I dont know which to select. >>>
You will have to tell us what the available options are ;-)
<<< I want to transfer files to my mobile with this. Is that possible >>>
It may be possible depending on the software available for file transfers between devices. Windows XP uses IrOBEX (Infrared Object Exchange) protocol by default.