I used This Tutorial – Click Here to teach me how to do the same thing in Paint Shop Pro.
Although it is for PSP5, it works perfectly in PSP7.4
I have made one modification though : –
I keep my watermark as a completely separate image, at the grey stage.
Then with both images open in PSP I copy the entire watermark into memory, switch focus to the picture and paste it as a new layer.
Then it is simply a matter of continuing with the tutorial.