Resizing scanned pictures?

i have a HP Photosmart C4200 TWAIN printer. it has a scanner/copier too. well, i'm trying to make a manga-style comic book and decided that i want each page have the dimensions of 516 x 804. i dont have photoshop. all i have is paint (that comes with the computer) and photoimpression 3.0. i'm trying to resize it on a program that doesnt make the pixels all blurry. currently, i think, photoimpression 3.0 is the only thing that does that on my computer. help? and if photoimpession wont work, are there any programs i can download free that does this? or can i just do it before i press scan? tyvm!