I'll try to find the screen size for you. But you can actually resize JPG files right in Paint (in Windows XP, anyway, as I think this is a new function for that old program).
START/PROGRAMS/ACCESSORIES/PAINT. Open the image, click IMAGE menu, then Stretch/Skew. Change the size, and it actually will resize the image. If you stretch it to some value less then 100, it'll resize and reshape based on the percentages you use.
I'll see if I can find the screen size.
A thing moderately good is not so good as it ought to be.
Moderation in temper is always a virtue,
but moderation in principle is always a vice.
Thomas Paine, "The Rights of Man", 1792