How did all hallows eve turn into the halloween we know today...?

Question

with people dressing up in costumes and kids going door to door asking for candy?

Answer 1

I was wondering that about 5mins ago ::P

Go on that wikipedia it helped me alot :) x

Answer 2

You will get many different answers on this.  Here is my contribution.  

The dressing in costume tradition has been attributed to the ancient custom of dressing up in frightning ways to scare away evil spirits or fey spirits (who may not necessarily be evil but certainly mischevious).

Treats (perhaps in the form of alcohol or food) were another way to keep the fey spirits appeased and were usually left at the doorstep or upon an altar as a 'dumb supper' for the deceased (being this is a holiday to honor or communicate with the dead).  

Many of the people would imitate the fairies and go from house to house begging for treats. Failure to supply the treats would usually result in practical jokes being visited on the owner of the house.

In an attempt to make the holiday seem less 'diabolical', it has been simplified over MANY YEARS and changed to be a celebration mostly kids indulge in.

A word to the wise, this isn't the only answer, there are many reasons why and how the holiday has changed over the years.

You might find answers closer to the actual root by researching pagan resources than christian ones...