In MS Paint, just click on "Image" and then
"Stretch/Skew."
You can only stretch by % though, so for enlarge, you input % more
than 100.
To reduce, just stretch by a % below 100.
I use ACDsee for pic viewing, so i use it for enlarge/reduce image
size also.
Using MS paint is troublesome if you want to reduce to exact
resolution, you need a calculator.....