I don't know what the file extension is for webcams pics- if they're other than the usual jpeg for instance.
But you should be able to open the photo program> go to File> New> browse to the location and choose the picture for editing. Windows Photo Gallery is a photo management, tagging, and editing tool that is included in Windows Vista.
I see this 'upgrade' mentioned: An upgraded version of Photo Gallery released under the Windows Live brand known as Windows Live Photo Gallery which can be downloaded from Windows Live Installer and also runs on Windows XP includes new features viewing color histogram of an image, panoramic stitching and auto-tagging during importing and also the ability to share photos by uploading them to Windows Live Spaces or Flickr.
This might be part of the problem: From Wiki: Windows Photo Gallery uses the Windows Imaging Component framework, that can be used by any codec to integrate with the image handling capabilities of the operating system and other applications that use WIC. Windows Vista ships with codecs for common formats like BMP, JPG, PNG, TIFF and HD Photo. However, GIF images do not appear in the gallery.
It may be that the webcam doesn't save to a file extension handled by this program.