After installing the Image Resizer and CD Slideshow Powertoys for Windows XP I discovered that they would only work with Bitmap images. When I tried to use them with JPEG images they just didn't show up. Much research led me to the following on one of the Windows Newsgroups. I used the registry fix and now my Powertoys work as intended. Apparently either an update or some software install removes the necessary settings.
1) Try running this from a command prompt to restore your image settings: regsvr32 shimgvw.dll
2) To add the missing string values open the Start menu, choose "Run", type "regedit" and hit Enter. Using the tree control in Registry Editor, navigate to HKEY_CLASSES_ROOT\.jpg. With the highlight on ".jpg", use the Edit menu , choose New/String value. Type in "Content Type" as the new value name then hit Enter. Double click the new value and type "image/jpeg". Repeat the last 2 steps to create a String value called "PerceivedType" and set its content to "image"