Resizing and format changing is usually the task of a Graphics editing proggy...from freeware such as Gimp to 'expensiveware' such as Photoshop ...

When resizing images from a small resolution to a larger resolution you will lose image quality.  Bit if you really need, you can open the image with windows paint program and on the home tab click on re size, then you can re size the image based on percent or you can change it by pixel.  I suggest using pixel, because you can choose the resolution of your monitor.   regardless of the program you use you are asking the program to compute how to fill pixels as the image increases in size and so the greater change in size will increase the diminishing quality of the image.  I am sure programs such as photoshop and paintshop pro will be better at re sizing images.  I suggest you find images that do not need to be re sized to a larger resolution, if anything find larger images to bring down to size.  Goodluck.

Cheers