Sorting files in Vista windows explorer problem

When using windows explorer I am used to sorting a folder with a large number
of files by date modified so that I can quickly access the most recently
modified files. However in Vista beta 2, things have changed. I have a large
number of zip files in this folder and explorer now groups all the zip files
first and sorts them by date modified, followed by all the other files in
date modified order. The XP version of explorer did not group the zip files
first and sorted all by date modified. Is there a way in Vista to sort all
the files by date modified and NOT have the zip files listed first as a
separate subgroup ? I have tried experimenting with the new Vista sorting
options "stack" and "group" but have been unsuccessful.