If you have too many files in a folder, or in search results, you can quickly narrow it down if you know when the file approximate date the file was modified.
In Explorer, hover your cursor over the Date Modified column. When the down-arrow appears, click it. Then, select the date ranges you want to see. Windows Vista filters the display to show only the files or folders in the selected range.

You can do this for any of the columns–Type and Date are also very useful.