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I have disconnected a smoke detector in my home that was wired into the burglar alarm using 4 wires because it kept going off despite the fact that there was no smoke.
I insulated all the wires that were loose and thought that would be OK, but now when I set my burglar alarm the zone that the smoke detector was connected to lights up and I have to omit this zone in order to set the alarm.

The terminals that the wires were connected to on the smoke detector were labelled: -

+12v
-12v
C
NC
Can anyone tell me what I need to do to stop this from happening?

BTW I have put up some new smoke alarms to replace this one.

Many thanks in advance.

Intruder alarms work by having detection devices that go "open" when they detect. (So a burglar can not cut the wire to bypass the alarm)
Since you have removed a smoke detector you have left the circuit "open" You need to connect the two wires that were on C and NC together.
Keep the other two apart, as they will be the 12v supply.