Windows XP has a thumbnail view which will provide a display of files in a folder as thumbnails. When it generates the thumbnails, it Windows generates a file called THUMBS.DAT which sits in that directory. not only does this take up hard drive space, but it can be annoying down the road when you try to choose another view (such as Details). Windows may still revert back to thumbnails no matter if you want to view details. This is happening because THUMBS.DAT is present in that directory. Delete it and it won’t happen again. However, you can keep this from ever happening very easily. In Explorer, go to Tools / Folder Options, choose the View tab, and then turn off the “Do not cache thumbnails” option. Click OK.