Resize old pictures and burn new size to cd

I am trying to make a slideshow using media center. The photos I am using
are old and I am trying to scan them to 150% and 300dpi so they will be big
enough to use on a slideshow. I scan them on this setting and move the scan
to my pictures folder. When I try to save them to a cd I cannot burn the new
size?
Thanks for your help
Jonesy