How many pictures are in the folder ?
If it is hundreds or even thousands then maybe Windows is checking through them all and it is taking a long time.
Try perhaps putting the pictures in different folders, one folder for each event or occasion.
So you could have one folder for 2006 holiday, another for 30th birthday, another for 2005 Xmas and so on.
That way there will only be a few pictures in each folder.
Then Windows will not have to look through them all when you want to look at just one set of pictures.