Sounds like a H4 Headlamp bulb?!
Remove the connector from the blown bulb then pull the rubber gaiter off that surrounds the bulb and connector. Unclip the spring clips that hold the bulb into the lens (they are pretty awkward and stiff, you will probably end up with sore fingers). Fit the new bulb, clip the spring clips back into place, replace the rubber gaiter and reconnect the connector.
P.s. If it is drives side remove the filler neck from the washer bottle by lifting the clip at the base to give you more room.
Dan
May 2008