Sorting in Windows explorer problem

When using Windows explorer in Win/XP, I am used to sorting files in a large
folder by date modified so that I can quickly access the most recently
modified files. However, In Vista beta 2 things have changed. Now any zip
files (and I have a lot of zip files!) are listed as a subgroup first and
sorted within that subgroup, then followed by all the other files. In Win/XP
explorer there is no subgrouping of the zip files. Is there a way to sort all
files simply by date modified and not have the list broken up into subgroups
? I have tried experimenting with some of the new Vista explorer options
"group" and "stack" but have had no success !?