Use the Stretch/Skewer command (Ctrl + W) to reshape your image. But decreasing the size by that much will probably cause distortion. Which flag are you drawing by the way?
About IrfanView... I don't know it wasn't me who installed it! Do a net search on it... it'll be free otherwise we wouldn't have it...
. But any basic picture editor will be able to blur an image, though MS Paint can't.