... ok, guys, since I am working in DESIGN for quite some time now, I can say THERE iS NO SOFTWARE that can significantly enlarge ANY photo without pixelation.
Alien skin BLOWUp is a good one, I often use it. It can minimise jpeg artefacts, sharpen up photo, but, it also ADDS GRAIN to immage, and U can control how much.
Now, it is industry (design/print) standard, really, 'cause before ALIEN SKIN, we did just that: use median filter if it is scanned immage without descreening, fix colors, curves, unsharpmask-it, and then - add a little MONOCHROMATIC UNIFOM NOISE.
It just makes those blotchy, over-enlarged immages - viewable easier, and it looks better in print.