Thicket Files and Folders
How thickets are created
A folder with a name similar to pagename_files is a thicket folder. Thickets are created when content is created in Word, Excel, PowerPoint or Publisher and saved as HTML from those applications, or when VML graphics are used. (VML consists of WordArt, ShapeArt, Text-boxes or any objects created from the FrontPage or Office Drawing toolbar). Thickets are also created by Internet Explorer when saving a web page as HTML (complete).
The thicket folder contains supporting files, such as images, for the Web page. The folder uses the same name as the HTML file of the Web page, in the form pagename_files. This page/folder combination is known as a thicket. Thicket folders are always hidden in FrontPage and Expression Web.
In Windows Explorer, you can control how thickets are manipulated:
Tools->Folder Options
On the View Tag, look for "Managing pairs of Web Pages and Folders" and pick an option, the best option being "Show both parts and manage them individually".
If any changes are made in Windows Explorer, then make sure that FrontPage or Expression Web knows about them by opening the web site in FrontPage (or Expression Web) and running Tools->Recalculate Hyperlinks (Site->Recalculate Hyperlinks in Expression Web) to update the web's meta data.