If same as mine small hallogen spot lights both in my conservatory and bathroom they are held in by a ring clip. You should see two bent ends around the lense squeeze the ends towards each other and the ring will come away from the light and the hallegen bulb will drop out on it's cable. Pull the plug off the hallogen bulb. Replace with same rating in reverse of removal. If no ring and are mains they are twist or screw fit
Check the bulb rate & watts ie: 12v ?w or 230/40v ?w
The large mains type maybe screw fit.
Bob
March 2009