In Windows XP this is really easy.

Right click on an original image file in My Computer or Explorer and select properties.

Some tabs across the top, one is called Summary, click on it.

If there’s no information, then there may be a button marked Advanced, click on it.

If there is information, then there will probably be a button marked simple.

Note on the Simple view, you can add your own information, such as a title, subject, comments, etc…

The advanced view might be empty, if it isn’t an original unedited file. There are tools around that enable you to add exif data manually, do an Internet search for exif tools, or some such.