how do you take a down loaded picture of the net and in large it to an 8" x10"

[Jen]

clear picture? i have been making a picture list of items and have a bunch of pictures that are of different sizes and would like them all to be the same type (jpeg) and all the same sizes. 8" x 10" is to big, but it was a good size that everyone would know and also would make my point. the size i really would like is only about a 1/4 of this size. how would i go about doing this on my pc? also, i have down loaded a really good picture that i would like to have blown up to a poster size for my wall 41" x 27"; how do i go about blowing up a picture to a poster size?