How to remove gap between clustered columns?

I'm trying to produce a histogram with two series--my data and a Poisson distribution on the same chart. But I can't figure out how to remove the gaps between the clusters of columns. I'd like them to all run together continuously, to achieve something like this (made in Excel 2003):
<http://img441.imageshack.us/img441/3959/histogramkl3.jpg>

In 2008, all I can get is this:
<http://img149.imageshack.us/img149/2512/histogram2jf9.jpg>

This was relatively straightforward in 2003...IIRC, it was in Plot format under a field logically titled "Gap width". Can't figure it out for the life of me though in 2008. Any ideas? Thanks.