I used Format Factory which is a free tool to size down videos dimensions etc to play on my portable devices when traveling. You can select a aspect ratio or an X,Y screen size for it to size down to. Sizing down works great, but making videos larger, depending on how much stretching goes on at a certain point you will get pixel stretch making it fuzzy/blurry. Having a original video of larger and sizing down always works best, but making larger, pixels get stretched and so quality is lost the larger you go. You might be able to stretch it a small amount without loss with Format Factory. Another tool that might work but is used best for conversions is Virtual Dub. Although I know for a fact that Format Factory has more sizing features because its intended for portable device videos etc.
I have seen some youtube videos where people record video with their phones and then try to size it to make it bigger vs a video column and it loses lots of quality due to pixel stretch.
