Making images with 300 dpi

[snowforest]

Ok but after doing the way I suggested and saving and closing, when I check the image properties on windows, outside gimp, by right clicking on the image file name, I see that its dpi is now 300, which was my goal, so why does the method I suggest not work (either when I did it with scale or print size and both work) . I even opened the image now with irfan view for instance and saw that indeed its dpi is 300 , which was my goal. And resizing the image is ok, i can even do it easilly with MS picture viewer. After I obtain the 300 dpi image I just make it smaller with MS picture viewer etc... and thats it.