Well, if you have a PC with WIndows, Paint is right there in the accessories folder. And it's "free". You already paid for it when you bought a PC with Windows.

And it can't be easier to use.. just load it up, select stretch and skew, use the resize, use 50% for both settings, and resize it. If it doesn't fit, do it again on the reduced size photo until you have it the right size. Save it as JPEG (.JPG) and upload it. Couldn't be easier or cheaper.

CGr.