Assuming that you just have Paint, open up the image in paint, hit ctrl+w, and in the "stretch" part of the window enter 50 and 50 in the boxes labeled horizontal and vertical. Then save the image again. It should be 50% smaller.
If it's still too big just keep doing that.
Mom to rescued lady Anabelle and Harley, beagle mix mutt
"Saving just one dog won't change the world, but it surely will change the world for that one dog." - Richard C. Call
Lila Over the Bridge. RIP.