4 lights not working because of 1. how do i find it?

Not enough information Andy. Are these ceiling or worktop lights - are they normally switched or on a dimmer - are they mains or low voltage.

In the past - when you changed one light and all of them began to work again you probably re-made a bad connection purely by accident - a miracle happened!

It may well be that you have a wiring fault. It may be that all the lamps are good and it's just the wiring. The power and neutral wires will "daisy-chain" from one light fitting to another - if either Live or Neutral come adrift then all the downstream lights will stop working.

Take care and remember Hilare Belloc's poem about Lord Finchley...

Lord Finchley tried to mend the Electric Light
Himself. It struck him dead: And serve him right!
It is the business of the wealthy man
To give employment to the artisan.

Peccavi
October 2008