Microsoft Photo Editor is by default in Win98se the program that opens the Image files and it does resize.
Just go in Image -- Resize.
If you dont have Microsoft Photo Editor for an unknow reason. Theres always the good Paint program that you will find in the Start Menu in Program and in Accessoiries.
This one do very basic resizing and only accept some type of file(bmp,jpg,gif) you can always try other format.
To resize just open the picture and go in the Menu Image you will find the resize option.
Hope it helps